Diphenyl ether

Developmental toxicity / teratogenicity

Administrative data

Endpoint:

developmental toxicity

Type of information:

other: mixture of diphenyl ether (73.5%) and biphenyl (26.5%)

Adequacy of study:

key study

Study period:

1987

Reliability:

1 (reliable without restriction)

Rationale for reliability incl. deficiencies:

other: GLP, guideline study

Cross-reference

Cross-reference 1

Reason / purpose for cross-reference:

reference to same study

Cross-reference 2

Reason / purpose for cross-reference:

reference to other study

Data source

Reference

Reference Type:

study report

Title:

Unnamed

Year:

1987

Materials and methods

Test guideline

Qualifier:

according to guideline

Guideline:

OECD Guideline 414 (Prenatal Developmental Toxicity Study)

Deviations:

yes

Remarks:

Females were mated prior to sorting into groups.

Principles of method if other than guideline:

Not applicable

GLP compliance:

yes

Limit test:

no

Test material

Test material information

Constituent 1

Reference substance name:

Therminol VP-1 a mixture of biphenyl (26.5%) and diphenyl ether (73.5%)

IUPAC Name:

Therminol VP-1 a mixture of biphenyl (26.5%) and diphenyl ether (73.5%)

Details on test material:

Test Substance: Therminol VP-1 Heat Transfer Fluid
Supplier: Monsanto Company, 800 N. Lindbergh Blvd., St. Louis, MO 63767
Analysis: no data
Reference No.: Lot Number: NBP 30356734
Purity : Active ingredient is considered to be 100% for the purpose of formulating the dosing solutions. Test substance is a eutectic mixture.
Description/Appearance: Clear liquid
Expiration date: October, 1988

Test animals

Species:

rat

Strain:

Sprague-Dawley

Details on test animals or test system and environmental conditions:

Strain: CD@ (Sprague-Dawley derived)
Supplier: Charles River Breeding Laboratories, Inc., Portage, Michigan 49081
Justification for Animal Selection: Generally recognized standard laboratory rat. Bio/dynamics, Inc. has historical control data concerning the use of this strain of rat in teratology studies and data demonstrating the responsiveness of this strain of rat to a known animal
teratogen (i.e ., acetyl salicylic acid).
Received: 152 females
Placed on Test: 96
Date of Receipt: females 25 November 1986, males 20 May 1986 (proven breeders used solely for mating purposes; Bio/dynamics inhouse breeding colony)
Age at Receipt: 7 weeks for males and females
Acclimation Period: 14 days (females), 25 November-8 December 1986
Age at Initiation of Mating: 63 days (females), ~36 weeks (males)
Weight of Mated Females (Test Day 0): mean 241 gm (range 198-285 gm)
Housing: Individually, except during the first week of the acclimation period (two females/cage) and mating (one male and one female/cage) in stainless steel suspended cages with wire mesh floors.
Food: Purina Certified Rodent Chow No. 5002 (mash) fed ad libitum.
Water: Tap water delivered by automatic watering system, ad libitum
Contaminates: There are no known contaminants present in the food or water capable of interfering with the results of this study.
Photoperiod: 12 hour light/ dark cycle (7 AM to 7 PM) via automatic timer.
Temperature: Desired: 67-73°F, Actual : 72-76°F (Accl imation), Actual : 64-74°F (Test)
Relative Humidity: Recorded once daily (morning) . Desired : 30-70%, Actual : 40-81% (Accl imation), Actual : 43-86% (Test)
Identification: Each mated female rat was identified with a metal ear tag bearing its' animal number. This individual animal number plus Bio/dynamics' project number comprised a unique identification number.
Assignment to Groups: A sufficient number of female rats was received so as to discard unhealthy females prior to initiation of mating.
The population of animals received for study was evaluated for suitability to use on test by the staff veterinarian prior to the initiation of mating.
Females which mated were assigned to the groups daily in such a way as to most nearly equalize the Day 0 mean group body weights.

Administration / exposure

Route of administration:

oral: gavage

Type of inhalation exposure (if applicable):

other: Not applicable

Vehicle:

corn oil

Details on exposure:

Test article (Therminol@ VP-1 Heat Transfer Fluid) was administered via gastric intubation to mated female rats (24/group) from Days 6-15 of gestation. Dose levels were 50, 200 and 500 mg/kg/day and were derived from a pilot study conducted at this laboratory (86-3095). Included in this
study was a vehicle-treated (Mazola Corn Oil ) control group (24 mated females).


Dose volume: 5 ml/kg of body weight/day;initial dose volumes were derived from Day 6 body weights and were adjusted during the remaining treatment period to the most recent body wei ghts .

Dosing solutions were prepared fresh weekly and stored refrigerated in amber jars when not being used for dosing.

Pharmacy weighed out the appropriate amounts of test article directly into labelled 500 ml volumetric flasks with caps.Corn oil was added to each flask to full volume (500 ml) . Each flask was then capped and inverted several times. A magnetic stir bar was placed in each flask and the solutions were allowed to stir for at least 15 minutes. The solutions were stirred on a magnetic stir plate prior to dispensing into beakers for daily dosing.

Analytical verification of doses or concentrations:

yes

Details on analytical verification of doses or concentrations:

The concentrations of dosing solutions taken from each dose level were analyzed at each preparation interval. Samples were analyzed in duplicate.
Homogeneity and stability analyses were performed pre-test . Homogeneity analyses were performed on the low (Group II) dose and high (Group IV ) dose. Stability was determined for 8 days of storage under refrigeration for Groups II and IV .

Dosing solutions of Therminol VP-1 in corn oil are assayed using Gas Liquid chromatography. An aliquot of the dosing solution is dissolved in methylene chloride and then injected into a gas chromatograph. Therminol VP-1 is detected using a Flame Ionization Detector. Integrated peak areas normalized with an internal standard are used for quantitation.

LIMITS OF ASSAY: The limit of detection for this procedure is a response equal to two times the noise level using the instrument parameters.
The limit of quantitation for this procedure is that of a response equal to the response for the low standard used for calibration. No response
or responses less than the low standard are reported as a less than value ( < ) calculated as follows:
Concentration of low standard (ug/ml) x ( dilution factor ) x (.001 mg/ug)
102 ug/ml X 50 X 0.001= 5.10 mg/ml

Details on mating procedure:

Females selected for mating were placed with male rats nightly in a 1:1 ratio. Vaginal smears were taken early in the morning following intervals of nightly co-habitation and females were considered to have mated if sperm and/or a vaginal plug was observed. The day on which
evidence of mating was observed was defined as Day 0 of gestation.

The evenings for co-habitation of males with females, were scheduled to provide females at Day 20 sacrifice during the Monday-to-Friday work week. The number of females caged nightly was also controlled to limit the number of mated females sorted into groups on a particular day. In this study, the maximum number of mated females sorted into groups on a particular day was 16. When the number of females mated after an evening exceeded the number to be sorted among the groups that day, females excluded from the sorting procedure were determined using a random numbers t a b l e and the female's temporary cage card number.

Mating was conducted on twelve nights as follows:
9, 10, 12, 15, 16, 17, 18, 19, 22, 23, 24, 25 December 1986

Duration of treatment / exposure:

Days 6-15 of gestation

Frequency of treatment:

once a day

Duration of test:

20 days (females killed on day 20 of gestation)

Doses / concentrations

Doses / concentrations 1

Remarks:

Doses / Concentrations:
vehicle treated controls, 50, 200 or 500 mg/kg/day
Basis:
nominal conc.

Doses / concentrations 2

Remarks:

Doses / Concentrations:
Concentration of dosing solutions: 0, 10, 40 or 100 mg/ml
Basis:
nominal conc.

No. of animals per sex per dose:

24 mated females/group

Control animals:

yes, concurrent vehicle

Details on study design:

This study, conducted for Monsanto Company, was designed to meet requirements established by the United States Environmental Protection Agency according to published TSCA protocol guidelines as presented in 40 CFR, Volume 50, No. 188 (September 27, 1985) #798.4900. This study was also designed in general agreement with OECD guidelines (No. 414) with the only exception that females were mated prior to sorting into groups.

Data provided by the exami nation of fetuses recovered from mated female rats treated during the period of embryonic organogenesis were used to evaluate the embryotoxic, fetotoxic, and/or teratogenic potential of Therminol VP-1 Heat Transfer Fluid. Test article (Therminol VP-1 Heat Transfer Fluid) was administered via gastric intubation to mated female rats (24/group) from Days 6-15 of gestation. Dose levels were 50, 200 and 500 mg/kg/day and were derived from a pilot study conducted at this laboratory (86-3095). Included in this study was a vehicle-treated (Mazolaa Corn Oil) control group (24 mated females). Females were killed on Day 20 o f gestation and given a gross postmortem examination. Ovaries were evaluated for number of corpora lutea and uterine implantation data were evaluated for number of live, dead and resorbed fetuses. Fetuses recovered at this time were weighed, sexed and evaluated for external abnormalities; approximately one-half of the fetuses in each litter ( alternating fetuses within the litter ) were processed for soft tissue exami nation (microdissection procedure) and the remaining fetuses were processed for skeletal evaluations (Alizarin Red S) .

Examinations

Maternal examinations:

Physical observations- Twice daily (morning and afternoon) for signs of pharmacologic or toxicologic effects and mortality. In addition, each female was given a detailed physical examination on Days 0, 6, 10, 12, 15 and 20 of gestation. On Days 6, 10, 12 and 15 of gestation the detailed physical given post-dosing. Cage-side observations were performed once per day during the treatment period (Days 6-15).

Body weights- Recorded on Days 0, 6, 10, 12, 15 and 20 of gestation. Day 20 body weights are presented as actual and corrected (the actual Day 20 body weight minus the weight of the gravid uterus).

Food consumption- Recorded for the following intervals during gestation: 0-6, 6-10, 10-15-and 15-20.

Gross Postmortem Examinations- Complete gross postmortem examinations were performed on alll mated females including those dying spontaneously. External surface, all orifices, the cranial cavity, carcass, the external surface of the spinal cord and sectioned surfaces of the brain, nasal cavity and paranasal sinuses, the thoracic, abdominal and pelvic activities and their viscera and the cervical tissues and organs were examined for all animals. The carcass of each female was discarded at completion of the gross postmortem evaluation.

Ovaries and uterine content:

The intact uterus (ovaries attached) was removed from the abdominal cavity, weighed and the number and location of the following were recorded for each uterine horn: live fetuses, dead fetuses (no evidence of tissue degeneration), late resorptions (recognizable dead fetus undergoing degeneration regardless of size), early resorptions (evidence of implantatian but no recognizable fetus) implantation sites. The ovaries were dissected free from
the uterus and evaluated for the presence and number of corpora lutea. When no uterine implants were grossly apparent, the uterus was stained with
ammonium sulfide (method of Salewski ) . When no foci were visualized post-staining, the female was considered not pregnant.

Fetal examinations:

All fetuses were given a gross examination for external malformations/variations to include observation for palatal defects. Subsequently, each fetus was weighed and individually identified. The sex of each fetus was noted externally (ano-genital distance) and was confirmed,by internal inspection of the gonads at subsequent evaluation.

Approximately one-half of the fetuses in each litter (alternating fetuses within the litter) were evaluated for soft tissue malformations/variations using a microdissection procedure similar to that described by Staples. Evaluatlons were perfomed on fresh fetal specimens shortly after removal from the uterus. Fetuses designated for soft tissue evaluation were decapitated [head placed in appropriately labelled embedding bags ( i.e. , teabags) and fixed in Bouin's solution for later evaluation]. The fetal specimens were then secured beneath a dissecting microscope and dissected so as to permit evaluation of tissues in the thoracic and abdominal cavities. At the completion of the fetal examination, the fetuses were eviscerated (viscera discarded) and placed in individual plastic cassettes and stored in 70% ethanol solution. Following a period of fixation, the fetal heads were sectioned using a razor blade. The serial, transverse sections generated during this procedure were evaluated for malformations of the palate, eyes and brain under a dissecting microscope (10-20X). Following evaluation, head sections were placed in plastic cassettes for storage (one litter/jar ) in a 70% ethanol solution.

The remaining fetuses in each litter werekilled via lethal exposure to ether. The intact fetuses were eviscerated (internally sexed by inspection of the gonads) and processed for staining of the ossified skeletal structures using the Alizarin Red S staining procedure of Crary as modified by Bioldynamics.

Fetal skeletal specimens were evaluated under a dissecting microscope (10-20X) for ossification variations and malformations. Following evaluation, all fetuses were storedin plastic jars with plastic screw-on lids (1 litter/jar ) in a 50/50 solution of 70% ethanol and 100% glycerin.

Late resorptions were examined grossly for external malformations and discarded.

Statistics:

Data were analyzed between control (Group I) and treated groups (Groups II-IV).

Statistics Cont'd below (any other information on materials and methods)

Indices:

See below (any other information on materials and methods)

Historical control data:

No data

Results and discussion

Results: maternal animals

Maternal developmental toxicity

Details on maternal toxic effects:

Maternal toxic effects:yes

Details on maternal toxic effects:
Mortality
No mortality occurred in the control or low-dose groups and all females in these groups survived to scheduled sacrifice. In the mid-dose group
(200 mg/kg/day), one female died ( mortality rate = 4.2%) and in the high-dose group (500 mg/kg/day) , two females died ( mortality rate = 8.3%).

Mid-dose female No. 3511 was found dead on Day 8 of gestation. Gross postmortem examination revealed a perforation in the trachea and death
was attributed to a dosing injury. Thus, no treatment-related mortality was seen at the mid-dose level.

High-dose female No. 4503 died on Day 11 of gestation after receiving five days of treatment. High-dose female No. 4525 also died on Day 11 of gestation but had received six days of treatment. A common postmortem finding for both high-dose animals that died was staining of the fur in the ano-genital (A-G) area. Death of these females was considered to be treatment related. No evidence of intubation error was seen in these high-dose animals.

Pregnancy Rates
Pregnancy rates were 91.7% (22/24 females pregnant) in the control and mid-dose groups and 100% in the low- and high-dose groups. These rates
were considered comparable between the control and treated groups.

Body Weights - Gestation Period
Mean body weights at each recorded interval during gestation were comparable between the control, low- and mid-dose groups. In the high-dose group, mean body weights were slightly lower than control at Days 10, 12 and 15 (-6.4%, -5.7% and -7.0%, respectively) of the treatment period and continued to be depressed at Day 20 (-3.5%); however, only at Day 15 was this difference from a control statistically significant.

Mean weight gain during the treatment period (Days 6-15) was lower than control in each of the treated groups (-13.0%, -19.8% and -44.2% for the
low-, mid- and high-dose groups, respectively); however, only at the mid- and high-dose levels were these differences from control statistically significant. Mean weight gain for the pre-treatment (Day 0-6) and post-treatment (Day 15-20) intervals of gestation were considered comparable between the control and treated groups.

Mean weight gain for the Day 6-20 gestation interval using the corrected Day 20 body weights were lower than control in each of the treated groups (-13.2%, -21 .l% and -36.4% for the low-, mid- and high-dose groups, respectively); however, only for the mid- and high-dose groups were these differences from control statistically significant. Mean gravid uterine weights and corrected Day 20 body weights were considered comparable between
the control and treated groups.

Thus, at all dose levels, a decrease in mean weight gain was seen during the treatment period (Days 6-15) and for the Day 6-20 gestation interval
using the corrected Day 20 weights; however, only at the mid- and high-dose levels (200 and 500 mg/kg/day) were these differences from control statistically significant.

Food Consumption - Gestation Period
Mean food consumption was comparable between the control and low dose group over each recorded interval of the study. In the mid- and high-dose groups, mean food consumption was statistically significantly lower than control during each recorded interval (Days 6-10 and 10-15) through the treatment period. During pre- and post-treatment intervals, mean food consumption for the mid- and hi gh-dose groups was comparable to control.
Thus, only at the mid- and high-dose levels was an adverse effect of treatment evident from a decrease in food consumption during the treatment period.

Physical In-Life Observation Data
Physical observation data were similar between the control and low dose group.

In the mid- and high-dose groups, excessive salivation, staining of the skin/fur in the ano-genital area { i.e. , A-G Stains) and alopecia were all seen with increased incidence. Excessive salivation was seen in a total of three mid-dose and nine high-dose females during the treatment period; this observation was not seen among the control or low-dose females. A-G stains were seen in four mid-dose and eight high-dose females during the treatment period; this observation was also seen in one control female.

Areas of alopeci a were noted among animals in all study groups during the treatment and post-treatment intervals. The incidences of females
with alopecia initiating during the teatment period or only a t Day 20 (posttreatment) for the control, low-, mid- and high-dose groups were 4/24 (16.7%), 5/24 (20.8%), 8/24 (33.3%) and 14/24 (58.3%), respectively. The increased incidence of females with alopecia at the mid- and high-dose levels may be suggestive of a treatment-related effect.

Thus, only a t the mid- and high-dose levels were adverse effects of treatment evident from the detailed physical evaluations. Observations seen
with increased incidence among these groups were excessive salivation , A-G stains and alopecia.

Corpora Lutea and Uterine Implantation Data
The mean numbers of corpora lutea, uterine impl antations, viable fetuses and resorptions per pregnant female were comparable between the control and treated groups. Likewise, the mean pre-implantation loss index and mean resorption/implant ratio were comparable between the control and treated groups. The incidence of females with resorptions among, their uterine implants was also comparable between these
same groups.
No adverse effects of treatment at dose levels up to 500 mg/kg/day were evident from uterine implantation data.

Gross Postmortem Observations
Hair loss ( i.e., alopecia) was evident in a number of animals in different anatomical sites with increased incidence in Group IV (500 mg/kg/day)
Other postmortem findings observed grossly occurred sporadically and were not considered to be related to the test article.

Effect levels (maternal animals)

1

Dose descriptor:

NOAEL

Effect level:

500 mg/kg bw/day (nominal)

Basis for effect level:

other: developmental toxicity

2

Dose descriptor:

LOAEL

Effect level:

50 mg/kg bw/day (nominal)

Basis for effect level:

other: maternal toxicity

Results (fetuses)

Details on embryotoxic / teratogenic effects:

Embryotoxic / teratogenic effects:no effects

Details on embryotoxic / teratogenic effects:
Fetal Body Weights
Mean fetal weights, as a composite for both sexes and when distinused by sex, were comparable between the control and treated groups.
No adverse effect of treatment was evident from fetal weight data.

Fetal Sex Distribution Data
The mean number of male and female fetuses per female and the ratio of total male/female fetuses per group were comparable between the control
and treated groups.
No adverse effect of treatment was evident from fetal sex distribution data.

Fetal External Examination Data
a. External Malformations
No external malformations were seen among fetuses in Groups I (control - 316 fetuses evaluated from 22 litters ) , III (200 mg/kg/day - 313
fetuses evaluated from 21 litters ) or IV (500 mg/kg/day - 329 fetuses evaluated from 22 litters ) In Group II (50 mg/kg/day) , the incidence of fetuses with external malformations was 0.6% (2/352 fetuses), The incidence of Group II litters containing fetuses with external malformations was 8.3% (2/24 litters).
In the low-dose group, one fetus (No. 10) from the litter of female No. 2514 did not have a lower jaw (i.e., agnathia) , A second low-dose
fetus (No. 2) from the litter of female No. 2517 had a small lower jaw (i.e., microynathia) and was edematous. At skeletal examination the lower jaw of this fetus did not appear shortened; the distortion in jaw shape noted externally was apparently attributed to the edematous condition. No other external malformations were seen in the remaining 350 fetuses (total 24 litters) evaluated at this dose level.
In the absence of similar defects among fetuses at the higher dose levels, the occurrence of two fetuses with malformations in the low-dose
group was not considered indicative of a treatment-related effect.

b. External Variations
No external variations were seen among fetuses at the mid- and high-dose levels. In the control and low-dose groups, the incidences of fetuses
with external variations were 0.6% (2/316) and 0.3% (1/352), respectively.
No adverse effect of treatment was evident from fetal external variation data.

Fetal Sex Distribution Data
The mean number of male and female fetuses per female and the ratio of total male/female fetuses per group were comparable between the control
and treated groups.
No adverse effect of treatment was evident from fetal sex distribution data.

Fetal Visceral Examination Data
a. Visceral Malformations:
The incidences of fetuses with visceral malformations for the control, low-, mid- and high-dose groups were 1.2% (2/163 fetuses), 0.5% (1/183
fetuses), 0.6% (1/161 fetuses) and 0% (0/169 fetuses) , respectively. The incidences of litters containing fetuses with visceral malformations for the
control, low-, mid- and high-dose groups were 9.1% (2/22 litters) , 4.2% (1/24 litters) , 4.8% 1/21 litters) and 0% (0/22 litters) , respectively. These
incidences were considered comparable between the control and treated groups.
A low incidence of dissimilar visceral malformations was seen among the treated groups. No adverse effect of treatment was indicated.

b. Visceral Variations:
Visceral variations involve subtle changes in the size, shape or appearance of the visceral organs/tissues. These types of observations are
considered to represent transient developmental stages. Such changes are not considered indicative of malformation, but an increase in incidence o f fetuses with certain visceral variations when seen to occur in a dose-related pattern may be indicative of a fetotoxic response to treatment ( i .e., delayed development) .
The incidences of fetuses with visceral variations for the control , low-, mid- and high-dose groups were 4.3% (7/163 fetuses), 1.6% (3/183
fetuses) , 0% (0/161 fetuses) and 0.6% (1 /I69 fetuses) , respectively . The incidences of litters containing fetuses with visceral variations for
the control, low-, mid- and high-dose groups were 18.2% (4/22 litters) , 12.5% (3/24 litters) , 0% (0/21 litters) and 4.5% (1/22 litters) , respectively. The only statistically significant difference in these incidence data involved the absence of fetuses with visceral variations at the mid-dose level.
No adverse effect of treatment was evident from visceral variation data.

Fetal Skeletal Examination Data
a. Skel etal Malformations
The incidences of fetuses with skeletal malformations for the control, low-, mid- and high-dose groups were 1.3% (2/153 fetuses), 1.8% (3/170
fetuses), 0.7% (1/152 fetuses) and 0.6% (1/759 fetuses), respectively. The incidences of litters containing fetuses with skeletal malformations for the
control, low-, mid- and high-dose groups were 4.5% (1/22 litters) , 12.5% (3/24 litters), 4.81 (1/21 litters) and 4.5% (1/22 litters) , respectively. These incidences were comparable between the control and treated groups. A low incidence of dissimilar skeletal malformations was seen
among the treated group fetuses. No adverse effect of treatment was evident from these data.

b. Ossification Variation Data:
Ossification variations may represent delays in the ossification process (retarded ossification) or slight ossification irregularities which may or may not be present in the adult specimen. Ossification variations are not considered representative of malformation but an increase in the
incidence of fetuses with ossification variations or an increase in the incidence of fetuses with a particular ossification variation may be suggestive
of retardation in ossification which could be regarded as a fetotoxic response to the test material.

The incidences of fetuses with at least one ossification variation for the control, low-, mid- and high-dose groups were 60.8% (93/153
fetuses), 61.8% (105/170 fetuses), 67.2% (93/152 fetuses) and 60.4% (96/159 fetuses), respectively. These incidences were comparable between the control and treated groups.

Ossification variation data by type and incidence of fetuses affected were considered comparable between the control and treated groups. Rudimentary rib structures adjacent to the first lumbar vertebra transverse process(es) were seen with increased incidence in respect to the concurrent
control group among the mid-dose fetuses and to a lesser extent in the low-dose group. Rudimentary rib structures are a commonly seen ossification variation a t this laboratory. A review of ossification variation data for recently completed rat teratology studies conducted at thi laboratory showed the overall incidence of rudimentary structures in control fetuses to be 5.6% with a range of values for individual studies of 0.6% to 20.3%. The incidence of rudimentary rib(s) for the concurrent control, low- and high-dose groups (5.2%, 11.8% and 8.2%, respectively) were well within the range of recent historical control data and the incidence for the mid-dose group (20.4%) was at the high end for this range (i.e., 20.3%). In the absence of a dose relationship in regard to the incidence of fetuses with rudimentary first lumbar rib (s) among the treated groups, no adverse effect of treatment was indicated.
Thus, no adverse effect of treatment was evident from ossification variation data.

Fetal abnormalities

Abnormalities:

not specified

Overall developmental toxicity

Developmental effects observed:

not specified

Any other information on results incl. tables

Analytical Results - Dosing Formulations

Analyses of homogeneity, stability and recovery samples for the dosing solutions all fell within a range of +/- 10% of the nominal concentration. Actual

analytical results for all samples collected were no less than 99.2% nor greater than 106%.

Applicant's summary and conclusion

Conclusions:

Therminol VP-1 Heat Transfer Fluid administered by gastric intubation to pregnant female rats during the period of embryonic organogenesis
(Days 6-15 of gestation) produced some evidence of maternal toxicity at all dose levels evaluated (50, 200 and 500 mg/kg/day). At the 50 mg/kg/day dose level, maternal toxicity was indicated by slight decreases in mean weight gain during the treatment period (Days 6-15) and for the Day 6-20 gestation interval using the corrected Day 20 weights; in both instances these differences from control data (-13.0% and -13.2%, respectively) were not statistically significant. At the 200 and 500 mg/kg/day dose levels, mean weight gain for the Days 6-15 and 6-20 gestation intervals were statistically significantly lower than control data and mean food consumption over the treatment period (Days 6-10 and 10-15) was also depressed (differences from control were statistically significant). During the physlcal evaluations, the incidences of females with excessive salivation, staining of the fur in the ano-genital area and/or alopecia during the treatment and post-treatment period were also increased.

At these same dose levels (50, 200 and 500 mg/kg/day) , Therminol VP-1 Heat Transfer Fluid was not considered to be embryotoxic, fetotoxic or teratogenic in the rat.

Executive summary:

This study was conducted for the Monsanto Company to assess the maternal toxic, embryotoxic, fetotoxic and/or teratogenic potential of Therminol VP-1

Heat Transfer Fluid in the pregnant rat. Test article was mixed in corn oil vehicle and administered by gastric intubation to mated female CD rats (24

mated females/group) from Day 6-15 of gestation. Dose levels were 0 (vehicle treated control), 50, 200 and 500 mg/kg/day. These dose levels were derived

from a pilot study conducted at thi s laboratory (Bio/dynamics Project No. 86-3095; Monsanto No. 88-86-378). During gestation, animals were observed twice

daily for mortality / morbidity and overt toxicological effects. Additionally, animals were weighed and given detailed physical evaluations periodically during gestation. Food consumption was recorded throughout gestation (Days 0-6, 6-10, 10-15 and 15-20).

On Day 20 of gestation, all surviving females were killed and given a gross postmortem examination. The uterus with ovaries attached was removed and weighed. Corpora lutea were counted for each ovary and uterine implantations were identified as live, dead or resorbed fetuses. Each fetus was weighed, sexed and evaluated grossly for external malformations. One-half of the fetuses in each litter were evaluated for visceral malformations (fresh microdissection procedure) and the remaining fetuses were eviscerated and processed for staining of the skeletal structures ( Alizarin Red S) and subsequent evaluations.

No mortality occurred in the control or low-dose groups. In the mid-dose group, one female died; however, this mortality was related to an intubation injury and was not considered treatment-related. In the high-dose group, two females died (mortality rate = 8.3%) on Day 11 of gestation and these deaths

were considered to be treatment-related.

At all dose levels, a decrease in mean weight gain was seen over the treatment period (Days 6-15) and for the Day 6-20 gestation interval using the corrected Day 20 weights; however, only in the mid- and high-dose groups were these differences from control statistically significant. No other maternal

toxicity was seen at the low-dose level .

Food consumption during the treatment period (Days 6-10 and 10-15) was decreased at the mid- and high-dose levels and these differences from control were statistically significant.

During the detailed physical examinations, the incidences of females with excessive salivation, staining of the skin/fur in the ano-genital area and/or alopecia were- increased in the mid- and high-dose groups.

No embryotoxicity or fetotoxicity was indicated at any of the dose levels evaluated (50, 208 or 500 mg/kg/day). Similarly, external, visceral and skeleta1 evaluations of fetuses recovered from females treated at these dose levels did not indicate an increase in malformation rate.

Thus, Therminal VP- 1 Heat Transfer Fluid administered to pregnant CD rats during the Day 6 -15 gestation period at dose levels of 50, 200 and 500

rng/kg/day was not considered to be embryotoxic, fetotoxic or teratogenic. Some maternal toxicity was seen at the 50 mg/kg/day dose l eve1 as evidenced by a slight decrease in mean weight gain during the treatment period and over the Day 6-20 gestation interval; however, these differences from control were not statisticlly significant. At the higher dose leve1s (200 and 500 mg/kg/day) , obvious maternal toxicity was seen by statistically significant reductions in mean weight gain during gestation (Days 6-15 and 6-20) and food consumption (Days 6-10 and 10-15). Females in these groups also showed an increased incidence of excessive salivation, staining of the skin/fur in the ano-genital area and alopecia.