Steroid regulation of luteinizing hormone secretion in normal and androgenized rats at different ages.

Abstract

Although sexual differences in the neural regulation of luteinizing hormone (LH) secretion are determined neonatally in the rat, these differences do not appear until adulthood in female rats given low doses of testosterone propionate (TP) neonatally (the delayed anovulation syndrome, DAS). To characterize this loss of the capacity for cylic LH release, the ability of gonadal steroids to induce a surge of LH at different ages in normal, DAS (10 μg TP, day 5) and anovulatory fully androgenized (FAS, 30 μg TP, day 2) female rats was tested under two conditions. In a short-term test conducted at 30 or about 120 days of age, rats were ovariectomized at 1000 h and given 5, 1, 0.5, 0.1 or 0.05 μg estradiol benzoate (EB)/100 g or oil 48 h later. Blood samples were taken 24 (1000 h), 31 (1700 h) and 55 (1700 h) h later. After three to four weeks, these same animals were given 8, 4 or 1 μg EB/100 g or oil at 1200 h and 2 mg progesterone (P) 72 h later. Blood was taken in this long-term test in three afternoon samp...