Steroid production by amago salmon (Oncorhynchus rhodurus) testes at different development stages |
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Authors: | N Sakai H Ueda N Suzuki Y Nagahama |
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Institution: | Noto Marine Laboratory, Kanazawa University, Ishikawa, Japan. |
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Abstract: | Developmental changes in the steroidogenic capacity of amago salmon (Oncorhynchus rhodurus) testicular fragments at six different stages during spermatogenesis and spermiation were examined using 18-hr incubations. Although both basal and chum salmon gonadotropin (SGA)-induced production of 11-ketotestosterone (11-ketoT) and 17 alpha,20 beta-dihydroxy-4-pregnen-3-one (17 alpha,20 beta-diOHprog) remained relatively low in testicular fragments isolated in August (GSI 1.06; primarily spermatocytes and spermatids in the testes) and September (GSI 2.33-4.85; many spermatids and spermatozoa in the testes), 11-ketoT production was two to three times higher than 17 alpha,20 beta-diOHprog production. In mid October (GSI 4.31; primarily spermatozoa in the testes, with a few spermatids remaining), SGA greatly stimulated 11-ketoT production with no further stimulation in late October (GSI 3.54; advanced spermiation). In contrast, SGA dramatically increased 17 alpha,20 beta-diOHprog production in late October and November (GSI 3.02), coincident with the period of active spermiation. A time course study showed that SGA caused a marked increase in production of 17 alpha,20 beta-diOHprog within the first 3 hr. Testes collected in August and September produced a considerable amount of 17 alpha,20 beta-diOHprog in the presence of an exogenous precursor, 17 alpha-hydroxyprogesterone. These results indicate that a shift in steroidogenesis from 11-ketoT to 17 alpha,20 beta-diOHprog occurs in the amago salmon testis immediately prior to or during the spermiation period and further suggest that mechanisms of gonadotropin action on 17 alpha,20 beta-diOHprog production in testes differ from those of ovaries (Y. Nagahama, 1987, Dev. Growth Differ. 29, 1-12). |
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