MODULATION OF TESTICULAR ANDROGEN PRODUCTION IN ADOLESCENT AFRICAN CATFISH (CLARIAS-GARIEPINUS)

At 6 months of age the first spermatozoa appear in the testes of the A frican catfish considered to be adolescent, since the development to a dulthood (12 months of age) is accompanied by further morphological an d functional differentiation of Leydig cells. There are increasing pla sma levels of 11-ketotestosterone (11-KT) and an increasing responsive ness to luteinizing hormone (LH) of testicular androgen secretion in v itro. Whether treatment of adolescent males with key hormones of the b rain-pituitary-gonad axis [gonadotropin-releasing hormone (GnRH), LH, and 11-KT] affects the testicular steroidogenic response to a challeng e with LM in vitro 7 days later has been investigated. Injection of Gn RH (2.5 mu g chicken GnRH-11 per kilogram of body weight), LH (25 mu g /kg), or a high dose of 11-KT (50 mu g/kg) downregulated basal and LH- stimulated testicular androgen secretion to a minimum of 35% of contro l values. Treatment with LH was, moreover, associated with changes in the ultrastructure of Leydig cell mitochondria which were either swoll en and had a less elect-ion-dense matrix or showed an elongated shape, Conversely, a moderate dose of 11-KT (20 mu g/kg) enhanced LH-stimula ted, but not basal, androgen secretion in vitro to a maximum of 190% o f control values. in view of the generally low LH plasma levels and of the steadily increasing 11-KT plasma levels during puberty, 11-KT may be involved in the up-regulation of the testicular steroidogenic capa city observed during development to full maturity. (C) 1997 Academic P ress.