The metabolism of 16-androstenes in boar salivary glands

Abstract

The metabolism of 5α-[5α- 3H]androst-16-en-3-one and [7α- 3H]androsta-4, 16-dien-3-one by minces of boar submaxillary and parotid glands has been studied. Both ketones were reduced to mixtures of 5α-androst-16-en-3α- and -3β-ols by submaxillary gland tissue and to the 3α-alcohol by parotid gland tissue. Control incubations using boiled salivary gland tissue resulted in little or no reduction of the two ketones. The capacity of submaxillary gland to reduce both 5α-[5α- 3H]androst-16-en-3-one and [7α- 3H]androsta-4,16-dien-3-one was greater than that of parotid tissue. The reduction of 5α-[5α- 3H]androst-16-en-3-one to 5α-androst-16-en-3α-ol by submaxillary tissue required NADPH but reduction to the 3β-alcohol required NADH. When boar saliva was incubated with 5α-[5α- 3H]androst-16-en-3-one, no reduction to the corresponding alcohols occurred, indicating the absence of 3-hydroxysteroid dehydrogenases in this fluid. No 16-androstenes were formed from [4- 14C]pregnenolone, [4- 14C]-testosterone or [4- 14C]dehydroepiandrosterone incubated with boar submaxillary and parotid tissue but 17β-hydroxy-5α-androstan-3-one was formed from labelled testosterone. Chemical analysis of boar submaxillary glands showed that they contained relatively large amounts of 16-androstenes, testosterone and 17β-hydroxy-5α-androstan-3-one, whereas in the parotid androgens were absent and only traces of 16-androstenes were found. The relative concentrations of 16-androstenes were 5 α-androst- io- en-3 α-ol > 5 α-androst-16-en-3-one > 5 α-androst-16- en-3 β-ol > 5, 16-androstadien-3 β-ol. Pathways for the biosynthesis of 5α-androst-16-en-3α- and 3β-ols are presented and discussed.