EFFECT OF TEMPERATURE ON THE TESTICULAR STEROIDOGENIC ENZYMES OF THE RAINBOW-TROUT, SALMO-GAIRDNERI

Testes of the rainbow trout, Salmo gairdneri, have been incubated with [3H]testosterone, [3H]androstenetrione, and [3H]pregnenolone at a range of temperatures from 1 to 37°. With testosterone and androstenetrione as substrates, yields of free 11-oxygenated androgens were maximal between 6 and 21°. Yields of steroid glucuronides however were highest between 21 and 31° with both substrates. It is suggested that one function of the high steroid glucuronide production by the teleost testis is to limit free 11-oxygenated androgen production to the environmentally favorable temperature for reproduction for the species. This may be achieved by removal of substrate and/or product as its glucuronide ester at higher temperatures. With pregnenolone as substrate, the major product was 17α,20β-dihydroxy-4-pregnen-3-one which was formed in maximal yield between 16 and 26°. With this substrate, only small amounts of glucuronides were isolated and it is suggested that this temperature/yield curve, which is very similar to that of total (free + glucuronide) 11-ketotestosterone obtained from androstenetrione, may be the characteristic curve for steroid synthesis in the absence of glucuronidation. © 1979.