Effects of 2,3,7,8-tetrachlorodibenzo-p-dioxin on testicular function in premature rats.

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We examined effects of persistent low and high dose of TCDD on testicular function in premature rats. 1) Effect of very low dose of TCDD administered to maternal rats on gonadal function of neonatal rats.We injected into maternal rats extremely 10 ng/kg of TCDD once a week from the time before the sex differentiation of fetus to the end of breast feeding, and observed the change in gene expression of testis and liver of the male offspring. 21days after birth neonatal rats ware subjected. Results : Testicular weights were increased at 3 weeks, but reduced at 6weeks in TCDD-treated rats. In morphological examination of testes there were no significant differences in cell numbers of germ cells, Sertoli cells and Leydig cells between controls and TCDD-treated rats at 3 and 6 weeks. The diameter of tubules were, however, significantly increased at 3 weeks in TCDD-treated rats. CYP1A1 mRNA in TCDD-treated rats was dramatically increased in the liver, not in the testis at 3 and 6 weeks. Compa … More red with control, the CYP1A1 mRNA expression were increased 10-fold at 3 weeks and 3-fold at 6 weeks in TCDD-treated liver. In contrast to CYP1A1, the levels of AhR and ARNT mRNA expression were not much influenced by the TCDD treatment. The expression of Inhibin alpha and beta-A mRNA in control testis decreased at 6 weeks, compared to those at 3 weeks. However TCDD did not alter the inhibin alpha, beta-A and beta-B mRNA expression at both 3 and 6 weeks. The level of ER alpha mRNA was statistically increased at 3 weeks in TCDD-treated testes compared with controls. There was no significant difference at 6 weeks between TCDD-treated testes and controls. Expression of ER beta was increased at 6 weeks in TCDD-treated testes, but not at 3 weeks. The TCDD treatment did not alter the level of testicular AR mRNA expression at 3 and 6 weeks. 2) Effects of high dose (1000 and 300 ng/kg/w from birth ot 8 weeks of age) of TCDD. Motility of sperm is decreased and abnormality of TCDD impairs testicular function, especially spermiogenesis. Less