EFFECT OF THE DAY OF ADMINISTRATION ON THE DEVELOPMENTAL TOXICITY OF TRIBUTYLTIN CHLORIDE IN RATS

The objective of this study was to determine the susceptible day for t he teratogenicity of tributyltin chloride (TBTCI) by a single administ ration on one of the days during organogenesis. Pregnant rats were giv en a single dose of TBTCI by gastric intubation at 100 mg/kg on either day 7, day 8, or day 9 and at 200 mg/kg on either day 7, day 8, day 9 , day 10, day 11, day 12, day 13, day 14, or day 15 of pregnancy. The maternal body weight gain in the period immediately following administ ration in all TBTCI-treated groups was significantly decreased. A sign ificant increase in the incidence of postimplantation loss was found a fter administration of TBTCI on day 7, day 8, and day 9 at 100 and 200 mg/kg and on day 10 and day 11 at 200 mg/kg. A significantly increase d incidence of fetuses with external malformations was detected when T BTCI was given on day 8 at 100 and 200 mg/kg and on day 11, day 12, da y 13, and day 14 at 200 mg/kg, and the most pronounced effect occurred after administration on day 13 of pregnancy. Cleft palate was observe d exclusively after administration during late organogenesis. It could be concluded that the manifestation and susceptibility of the develop mental toxicity of TBTCI vary with the developmental stages at the tim e of administration and that TBTCI has the biphasic sensitivity to ter atogenicity on day 8 and days 11-14 of pregnancy.