GROWTH-HORMONE, SEXUAL MATURITY AND STEROIDS IN MALE CARP (CYPRINUS-CARPIO)

Samples of pituitary, blood plasma and gonad were taken from male carp . The growth hormones (GH) in the pituitary and plasma were measured i n fish of various body weights (BW) and degrees of gonad development, and compared with the levels of 17 beta-estradiol (E-2), testosterone (T), 17 alpha-hydroprogesterane (17-P), 11-ketotesterone (11-KT) and p rogesterone (P) in the testes and plasma. The gonadosomatic index incr eased rapidly with BW from 100 to 600 g, and then decreased at 900 g. The pituitary GH did not change with BW, but plasma GH was higher in f ish weighing 300 +/- 50 and 600 +/- 50 g, than in fish weighing 900 +/ - 50 g. In fish weighing 150 +/- 50 to 300 +/- 50 g, the level of T ro se significantly in the testes (2.27 ng g(-1)) and plasma (1.3 ng g(-1 )); E-2 was very low in both testes (0-30 pg g(-1)) and plasma (11-28 pg ml(-1)), increasing as BW rose from 150 to 600 g. The level of P ro se mainly at BW of 300 +/- 50 and 600 +/- 50 g: from 0 to 25 ng g(-1) in the testes and from 0 to 17 ng ml(-1) in the plasma. The level 17-P rose from 2.5 to 20 ng g(-1) in the testes at 600 +/- 50 g BW, but no significant change was recorded in the plasma. The level of 11-KT ros e significantly in the testes of fish at 300, 600 and 900 g (0.5-6 ng g(-1)). The application of different steroids (E-2, T and 17-P) on a p rimary culture of pituitary cells led to the release of GH. Release wa s significantly higher (P < 0.05) after 4 h at steroid concentrations of 10(-6) M. (C) 1998 Elsevier Science Inc. All rights reserved.