(1-hydroxyethylidene)bisphosphonic acid, potassium salt

Additional toxicological data

Administrative data

Endpoint:

additional toxicological information

Type of information:

experimental study

Adequacy of study:

supporting study

Study period:

No data

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

test procedure in accordance with national standard methods with acceptable restrictions

Data source

Reference

Reference Type:

publication

Title:

Relationship between bone mineralization, Ca absorption and plasma Ca in phosphonate treated rats

Author:

Treschel, U, Schenk, R, Bonjour, J-P, Russell, RGG and Fleisch, H

Year:

1977

Bibliographic source:

Am J Physiol, 232, E298 - 303

Materials and methods

Type of study / information:

Effects on bone.

Test guideline

Qualifier:

no guideline followed

GLP compliance:

no

Remarks:

pre-GLP

Test material

Test material information

Constituent 1

Reference substance name:

Sodium Salts of (1-Hydroxyethylidene)bisphosphonic acid (2-3 Na:1)

EC Number:

701-238-4

Molecular formula:

HEDP-2Na C2H6Na2O7P2 HEDP-3Na C2H5Na3O7P2

IUPAC Name:

Sodium Salts of (1-Hydroxyethylidene)bisphosphonic acid (2-3 Na:1)

Results and discussion

Any other information on results incl. tables

Neutralised HEDP (equivalent to 10 mg HEDP/kg bw) resulted in a significant (P<0.001) 3-fold increase in the width of the epiphyseal plate and inhibited mineralization of osteoid and cartilage (n = 38 animals).   

Uptake of 45Ca from ligated intestine was inhibited 40% by neutralised HEDP (P<0.001; n = 37 animals).  

Plasma calcium was increased 6% (P<0.001) after two subcutaneous injections of 10 mg-equivalent HEDP/kg bw/day, increased 26% (P<0.001) 1-hour after a third injection and increased 5% (P<0.001) 24-hour after a seventh injection (n = 34 - 39 animals). Plasma phosphate was decreased only 24 hours after the seventh injection (9% reduction; P<0.01; n = 34 - 37 animals). Epiphyseal plate width (P<0.001) and plasma calcium (P<0.001) were significantly increased, and intestinal calcium absorption decreased (P<0.001) in rats given 5 mg or 10 mg equivalent HEDP/kg/d (NOAEL = 2.5 mg/kg bw/day) (n = 12 rats/treatment).

Applicant's summary and conclusion

Conclusions:

In a well conducted study investigating the effects of HEDP-xNa on bone (reliability score 2), not conducted according to any OECD Test Guideline and pre-GLP study, male and female Wistar rats were given subcutaneous injections of 2.5, 5 or 10 mg/kg bw/day neutralised HEDP on seven consecutive days. Control animals were given an equal volume of saline alone. Blood was collected from the tails on Day 3 (one hour after injection) and Day 8 (24 hours after the final injection) to determine calcium levels. Following seven days of treatment, rats were anaesthetised following overnight fasting, and calcium absorption from the duodenum was estimated. Three frontal sections of the upper part of one tibia were prepared and the width of the epiphyseal plate measured (in triplicate). At a dose of 10 mg/kg bw/day, there was a significant (p<0.001) 3-fold increase in the width of the epiphyseal plate and inhibited mineralisation of osteoid and cartilage. Uptake from ligated intestine was inhibited 40% by neutralised HEDP (p<0.001). Plasma calcium increased by 6% (p<0.001) after 10 mg/kg bw/day, increased 26% (p<0.001) one hour after the third injection, and increased 5% (p<0.001) 24 hours after the seventh injection. Epiphyseal plate width (p<0.001) and plasma calcium (p<0.001) were significantly increased, and intestinal calcium absorption decreased (p<0.001) in rats given 5 and 10 mg/kg bw/day.
Therefore, decreased skeletal mineralisation was associated with decreased intestinal calcium uptake, hypercalcemia and increased epiphyseal plate width. A concluded NOAEL was determined to 2.5 mg/kg bw/day. The authors speculated that impaired intestinal calcium uptake is a secondary homeostatic response to the effect of neutralised HEDP on bone mineralisation.