INHIBITION AND MAINTENANCE OF SPERMATOGENESIS IN RATS IMPLANTED WITH POLYDIMETHYLSILOXANE CAPSULES CONTAINING VARIOUS ANDROGENS

Abstract

SUMMARY Polydimethylsiloxane (PDS) capsules providing surface areas of 50, 75, 100, 200, 400 and 2000 mm2 were filled with testosterone, testosterone cypionate (TC), or testosterone propionate (TP) and were implanted (s.c.) into sexually mature rats for 56 days to determine the efficacy of this mode of androgen administration in suppressing or maintaining spermatogenesis. Rats that received 75 mm2 capsules of TP and 200 mm2 capsules of testosterone or TC were azoospermic and had a 45–50% reduction in testicular weight. Moreover, immunoreactive serum luteinizing hormone (LH) and follicle-stimulating hormone (FSH) concentrations declined eightfold below control values, but plasma testosterone titres and the dry weight of the accessory sex glands were not affected (P > 0·10). Conversely, 2000 mm2 capsules of testosterone, TC or TP maintained testicular weight and induced accessory sex gland hypertrophy as well as a five- to eightfold increase in the concentration of plasma testosterone. The relative number of germ cells at stage VII of the cycle of the seminiferous epithelium was not affected (P > 0·15) by 2000 mm2 testosterone capsules even though immunoreactive serum LH and FSH concentrations remained at least eight-fold below control values. Similar implants containing TC or TP maintained germ cell numbers within 83% of control testes. The results establish that PDS capsules releasing 'low' doses of testosterone, TC or TP induce azoospermia without affecting plasma testosterone concentration or accessory sex gland weight, and that similar capsules releasing 'high' doses of testosterone maintained spermatogenesis quantitatively up to and including step 7 of spermiogenesis.