Effects of 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) on gonadal development in the chick embryo: a histological and histochemical study.

Fertile white Leghorn chicken eggs were exposed via intravitelline injections to dosages of 5.0, 10.0, or 20 mg 1,1-bis(p-chlorophenyl)-2,2,2-trichloroethane (DDT) in olive oil prior to incubation. Control embryos received only the olive oil vehicle. Eggs were placed in a forced-draft incubator for either 5 or 12 days. Embryos were removed and their gonadal areas prepared for histological or histochemical evaluation. Histological examination of DDT-exposed 5-day embryos revealed no significant differences in the number of primordial germ cells aggregating in the gonadal area and in the localization of acid and alkaline phosphatase activity. Embryos exposed to DDT for 12 days revealed significant alterations in both ovaries and testes. The testes of DDT-exposed embryos consisted of mostly stroma with fewer seminiferous cords than controls while ovaries of exposed embryos contained a larger number of distended medullary cords as well as a difference in the distribution of these cords when compared to controls. There was an increased alkaline phosphatase activity in the stromal cells of female gonads. Increased amounts of alkaline phosphatase activity found in the stroma at 12 days might be due to a DDT-induced stimulation of these cells to differentiate more rapidly. Acid phosphatase activity was found in the secondary sex cords of control 12-day ovaries, but was much reduced or absent in those of pesticide-exposed embryos. These results indicate that a single dosage of DDT administered to a chick embryo prior to incubation does not affect early stages of gonadal development but that effects on both ovaries and testes occur 12 days following exposure.