Morphological and biochemical alterations in reproductive tracts of neonatal female mice treated with the pesticide methoxychlor

Effects of estradiol-17 beta and the estrogenicity of different doses of the technical grade pesticide methoxychlor were compared in the vagina, uterus, and oviducts of neonatal mice. Beginning within 24 h of birth, neonates received 10 daily i.p. injections of sesame oil vehicle, 10.0 micrograms estradiol, or 0.05, 0.1, 0.5, or 1.0 mg methoxychlor. Estradiol injections induced precocious vaginal opening, complete vaginal cornification, and increased total reproductive tract weight and its DNA content. In comparison to the controls, the three highest methoxychlor doses also significantly increased the weights of the reproductive tracts and stimulated their development. The two highest doses (0.5 and 1.0 mg) also induced precocious vaginal opening and complete vaginal cornification. In addition, the same two doses produced atypical cells in the uterus and oviducts that may be indicative of early dysplasia; similar atypia were not recorded following estradiol treatments. Total DNA content in various reproductive organs increased with increased methoxychlor dosages. Dose-response changes were observed in the oviduct and uterus but not vagina. In summary, methoxychlor stimulated the development of neonatal female reproductive tracts, even at concentrations not previously reported to be biologically active. Furthermore, the higher doses induced abnormalities that were not seen following estradiol treatment; these abnormalities may represent precursors of pathological changes.