Sodium metaphosphate

Endpoint summary

Link to relevant study record(s)

Reference

Endpoint:

basic toxicokinetics in vitro / ex vivo

Type of information:

experimental study

Adequacy of study:

supporting study

Reliability:

2 (reliable with restrictions)

Rationale for reliability incl. deficiencies:

other: Meets generally accepted scientific standards, well documented, acceptable for assessment

Qualifier:

no guideline followed

Principles of method if other than guideline:

Water solutions of different sodium meta- and polyphosphates were incubated in isolated small intestine obtained from rat or pig. The resulting phosphate species were analyzed by the paper chromatography method according to Karl-Krupa (Anal. Chem. 1956, 28: 1091) with small modifications. Two-dimensional development was used to analyse of the samples.

GLP compliance:

not specified

Species:

rat

Strain:

Wistar

Details on species / strain selection:

Wistar male rats and pigs (sex not specified) were used.

Sex:

male

Details on test animals or test system and environmental conditions:

Adult male Wistar derived rats of about 250 g were fasted for 2 days to clear the intestine and then sacrificed with CO2. The small intestine was immediately excised and was flushed with 20 ml of warm saline and tied off into thee sections.Porcine small intestines were excised from hogs during slaughter at a local slaughter house and were taken to the laboratory. The first 2 m of each small intestine was used. These were flushed with 200 ml of warm saline and cut into 50 cm sections.

Route of administration:

infusion

Vehicle:

water

Duration and frequency of treatment / exposure:

24h

No. of animals per sex per dose / concentration:

not applicable

Control animals:

no

Preliminary studies:

not performed

Details on absorption:

not examined

Details on distribution in tissues:

not examined

Details on excretion:

not examined

Metabolites identified:

yes

Details on metabolites:

Hydrolysis of polyphosphates owas fast in in vitro rat intestine. In 60 minutes, metaphosphates with n>4 are substantially hydrolyzed. This rate suggests that enzymatic hydrolysis is likely to be involved, since for polyphosphates with n>4 at best marginal hydrolysis in water is reported at this pH.Porcine intestine also gave significant hydrolysis of both ring and chain phosphates. Summarizing, the rate of hydrolysis for each compound was similar to that in rat intestine. Identified metabolites comprised ortho-, pyro-, trimeta-, tripoly-, and tetrapolyphosphates.

Conclusions:

Linear as well as circular polyphosphates are hydrolysed in both rat and porcine small intestine. This reaction is mediated by enzymes of the brush border membrane. The resulting metabolite is mainly orthophosphate.

Executive summary:

Cyclic ring as well as linear polyphosphates including sodium trimeta-, tetrameta-, tripoly-, and hexametaphosphate were found to be enzymatically hydrolyzed in in vitro rat and porcine small intestine.

Sodium trimetaphosphate was reduced by 27.5% and 13.2% in rat and porcine small intestine after 1h, respectively. Sodium hexametaphosphate was reduced by 21.1% and 24.1% in rat and porcine small intestine after 1h, respectively. Sodium tripolyphosphate was reduced by 82.3% and 35% in rat and porcine small intestine after 1h, respectively.

The rate of hydrolysis in the in vitro intestine indicated an enzymic mechanism.

Description of key information

Supporting stud: The result of the study showede that linear as well as circular polyphosphates are hydrolysed in both rat and porcine small intestine. This reaction is mediated by enzymes of the brush border membrane. The resulting metabolite is mainly orthophosphate.