Neonatal androgenization in the male rat: evidence for central and peripheral defects

Studies were conducted to evaluate the development of the reproductive axis of the male rat androgenized with low-dose, chronic exposure to testosterone. Male rats were implanted with a testosterone-containing Silastic capsule on the day of birth. Capsules were left in the animals for 10 days, 20 days or permanently. Results indicate that in androgenized (A) rats, the weights of the testes (T), ventral prostate (VP) and seminal vesicles (SV) were significantly depressed in most age groups when compared to controls (C), regardless of the duration of capsule retention. Serum follicle-stimulating hormone (FSH), luteinizing hormone (LH) and prolactin (Prl) levels were not altered in adult (85 and 100 days old) A rats, but FSH and LH did show significant changes in young animals with testosterone-filled capsules. The efficacy of testosterone in promoting VP and SV growth, and increasing protein/DNA ratios in castrated A rats was significantly reduced compared to C rats, but it was increased with respect to suppression of LH secretion. Results suggest that a low, chronically administered dose of testosterone during the early neonatal period can produce permanent changes in the reproductive axis of the male rat and that these changes may be both central (hypothalamo-hypophysial) and peripheral (testes and accessory structures).