412 Identification of pesticides sex-specific gonadal toxicity

Abstract

While there are certain differences between biological responses to C-21 progestogens and the 19-norsteroids, precoital progestogens in general interfere with sperm transport, fertilization, and ovum transport. A 36 hour interval was required to achieve 100 per cent precoital contraceptive effectiveness in the rabbit. At marginal doses or timing, blastocyst degeneration may occur, and with large doses of progesterone at the time of coitus some teratogenic effects were noted. Postcoital estrogen is associated with lowering of plasma progesterone levels. Concomitant progesterone administartion, however, does not completely reverse the interceptive effect of estrogen. Direct effects on the endometrium include disintegration of the nucleolar channel system, retention of glycogen in endometrial glands, decreased alkaline phosphatase, and lowered endometrial carbonic anhydrase. The latter may be the basic mechanism of action.