THE EFFECT OF NEONATAL EXPOSURE TO DIETHYLSTILBESTROL, COUMESTROL, AND BETA-SITOSTEROL ON PITUITARY-RESPONSIVENESS AND SEXUALLY DIMORPHIC NUCLEUS VOLUME IN THE CASTRATED ADULT-RAT

The neonatal hormone enviroment influences the sexually differentiated patterns of development. Estrogens, derived from intracerebral aromat ization, promote mate pattern development of the central nervous syste m. The purpose of this study was to determine the effects of neonatal exposure to environmental estrogens on luteinizing hormone (LH) secret ion and development of the sexually dimorphic nucleus of the medial pr eoptic area (SDN-POA) in castrated adult rats. Neonatal rats of both s exes received injections of either corn oil, 0.1 mu g diethylstilbestr ol (DES), 3 mu g beta-sitosterol (B1), 30 mu g beta-sitosterol (B2), 0 .1 mu g coumestrol (C1), 1 mu g coumestrol (C2), or 10 mu g coumestrol (C3) on Day 1-10 of life and were castrated on Day 21. Right heart ca theters were placed on Day 42, and GnRH (50 ng/kg) was administered. B lood was sampled for LH at 0-, 5-, 10-, 15-, and 30-min intervals. All doses of beta-sitosterol and coumestrol elicited increased basal leve ls of LH in females. In males, B1, B2, C2, and C3 increased basal reve ls of LH. The GnRH-induced LH increase was prevented in females treate d with diethylstilbestrol and 10 mu g of coumestrol. Males in all trea tment groups exhibited GnRH-induced LH surges. The animals were sacrif iced by decapitation on Day 49. Volumes of the SDN-POA of the groups w ere compared. Treatment with the agents did not result in significantl y increased SDN volume in females; nor was there a difference in SDN s ize among the male groups. These data show that exposure to environmen tal estrogens early in development alters both postpubertal pituitary response to GnRH and basal LH secretion in females and alters only bas al LH secretion in males. No significant enlargement (i.e., masculiniz ation) of the SDN-POA was exhibited.