In vitro 11‐ketotestosterone and 17α,20β‐dihydroxy‐4‐pregnen‐3‐one production by testicular fragments and isolated sperm of rainbow trout, Salmo gairdneri

Two different testicular tissue preparations, testicular fragments and isolated sperm were incubated in the presence or absence of chumsalmon gonadotropin (SGA, lμg/ml), 17μ‐hydroxyprogesterone (17μ‐OHprog, 0.1 μg/ml) and testosterone (T, 0.1 μg/ml). 11‐Ketotestosterone (11‐keto T) and 17α,20β‐dihydroxy‐4‐pregnen‐3‐one (17α,20β‐diOHprog) in the incubation medium were measured by specific radioimmunoassay. Incubation of testicular fragments with SGA, 17α‐OHprog or T resulted in a highly significant increase in 11‐keto T levels in the incubation medium. Sperm preparations did not produce 11‐keto T under any incubation condition. Both testicular fragments and sperm preparations produced large amounts of 17α,20β‐diOHprog when incubated with 17α‐OHprog. SGA slightly stimulated 17α,20β‐diOHprog by testicular fragments but not by sperm preparations. These results suggest that different testicular elements are the sites of synthesis of 11‐keto T and 17α20β‐diOHprog. Furthermore, it is suggested the involvement of sperm in the production of 17α,2Oβ‐diOHprog in the testis of spermiating rainbow trout.