17α,20β,21-trihydroxy-4-pregnen-3-one and 17α,20β-dihydroxy-4-pregnen-3-one stimulated spermiation in protandrous black porgy, Acanthopagrus schlegeli

The objective of this study was to investigate the effects of sex steroids on spermiation in protandrous male black porgy, Acanthopagrus schlegeli. Experiments on common carp (Cyprinus carpio) were also conducted for comparison. Fifty male black porgy were divided into 5 groups and injected with a superactive analogue of mammalian luteinizing hormone releasing hormone (LHRH-A), 17 alpha,20 beta,21 -trihydroxy- 4-pregnen-3-one (20 beta-S), 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-DHP), 11-ketotestosterone (11-KT) or saline. The dosage of the sex steroids given on days 0, 2, 4 and 6 was 330, 330, 990 and 1980 mu g kg(-1) body weight, respectively. Milt volume and sperm concentrations were measured on days 0, 2, 4, 6, 8 and 10. Similar treatments were also conducted in 45 male common carp. Milt volume was significantly increased in black porgy after treatment with 20 beta-S and 17 alpha,20 beta-DHP; 17 alpha,20 beta-DHP had stimulatory effects on spermiation at a lower dose (900 mu g kg(-1) body weight, p < 0.05) as compared to 20 beta-S (1980 mu g kg(-1) body weight, p < 0.01). In the common carp, milt volume was also increased after treatment with LHRH-A and 17 alpha,20 beta-DHP but not with 20 beta-S. 17 alpha,20 beta-DHP stimulated spermiation at a lower dose in common carp (330 mu g kg(-1) body weight) than in black porgy (990 mu g kg(-1) body weight). However, 11-KT did not stimulate spermiation in black porgy or common carp. The concentrations of plasma 11-KT could immediately reflect to the administration of exogenous 11-KT in black porgy.