Studies on the Effects of Low Doses of 5α-Dihydrotestosterone (DHT) on the Basal Levels of Serum Gonadotropins and the Sensitivity of the Pituitary to Luteinizing Hormone Releasing Hormone (LHRH) in Adult Male Rats

Summary

Investigations were undertaken to study the effect of administering s.c. 10, 25, 50, 100, 500 and 1000 ng DHT/rat/day to normal adult male rats, for six weeks, on the basal levels of serum gonadotropin and the sensitivity of the pituitary to LHRH. The control group received olive oil. Animals were weighed and bled via cardiac puncture before the beginning of the treatment and weekly thereafter. After the last bleeding rats were injected intracardially 200 ng LHRH/rat and killed 15 min later. Blood, pituitary and testes were collected. Data were analyzed with respect to the control group and with respect to day zero of the treatment. DHT failed to produce a persistent effect on the serum gonadotropin. 10 and 500 ng DHT suppressed FSH levels significantly on days 21 and 7, respectively. 25, 50, 100 and 1000 ng DHT stimulated the release of FSH on day 42. 10 ng DHT reduced the levels of LH on day 14 of the treatment. 10, 25 and 50 ng DHT increased the sensitivity of the pituitary to release more LH in response to LHRH while 100, 500, 1000 ng DHT inhibited LHRH induced release of FSH. DHT at all doses tested failed to affect intrapituitary levels of LH and FSH. 10, 500 and 1000 ng DHT reduced the weights of the pituitaries as compared to the control group. The data demonstrate effects of DHT which are transient on the basal release of gonadotropins but are more persistent and differential on the sensitivity of the pituitary to LHRH.

Key-Words:

DHT - LH - FSH - Sensitivity - LH-RH - Pituitary - Feed Back