Tissue distribution of radioactivity was studied 48 h after gonadectomy and 1 h after iv injection of 3H-estradiol (1 μg/kg body wt) in 100- and 200-day-old normal female rats, female rats androgenized with 30, 100 or 1250 μg testosterone propionate (TP) at 5 days of age, and male rats. Receptor-mediated uptake of estradiol, as shown by diethylstilbestrol (DES) competition, was highest in preoptic area-anterior hypothalamus (POA-AH) and median eminence-basal hypothalamus (ME-BH), but also occurred in dorsal hypothalamus, prehypothalamic area, amygdala and septum in all groups. At 100 days of age there were no differences in brain radioactivity levels between females and androgenized females or males. At 200 days of age radioactivity levels in POA-AH and ME-BH tended to be lower in androgenized female and male rats than in normal females. Also, radioactivity levels in the amygdala were lower in the 1250 μg TP-treated females than in normal females. When expressed per unit fresh weight, uptake in the anterior pituitary tended to be lower in androgenized rats at 100 days of age and was higher in males at 200 days of age than in normal females, but did not differ among any of the groups when expressed as uptake per organ. Thus, the well-known differences among these groups in neural regulation of gonadotropin secretion and sex behavior were not correlated with consistent differences in specific estradiol binding by hypothalamic or other brain areas or pituitary. The uterus took up less estradiol in androgenized females than in control females at both ages. Estradiol receptor activity was demonstrated in kidney of all animals and in seminal vesicles. At both ages radioactivity levels in the toluene and ethanol extracts of liver and kidney were strikingly higher in males than in the female groups. Reviewing the data, it appears that despite some evidence of differences between groups, males, females and androgenized females all have relatively similar limited-capacity, estradiol-uptake systems in brain and pituitary, as measured under the conditions of the present study.
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