16-Unsaturated C19 3-oxo steroids as metabolic intermediates in boar testis

Abstract

1. The formation of the two 16-unsaturated alcohols 5α-androst-16-en-3α-ol and 5α-androst-16-en-3β-ol from [5α-3H]5α-androst-16-en-3-one has been demonstrated in boar testis homogenates. 2. The optimum yield (23%) of the 3α-alcohol was obtained in the presence of NADPH, whereas that for the 3β-alcohol (74%) was obtained when NADH was the added cofactor. 3. The two alcohols were not interconvertible. 4. Prolonged storage of boar testis tissue at −20°C abolished the ability to form all androst-16-enes except androsta-4,16-dien-3-one from [4-14C]progesterone. 5. The production of 5α-androst-16-en-3-one and the two alcohols from [7α-3H]androsta-4,16-dien-3-one only occurred when fresh tissue was used, whereas reduction of [5α-3H]5α-androst-16-en-3-one was unaffected by storage of testis at −20°C. 6. NADPH was the preferred cofactor for the reduction of androsta-4,16-dien-3-one. 7. The previously established conversion of androsta-5,16-dien-3β-ol into androsta-4,16-dien-3-one was shown to be reversible, NADH and NADPH being equally effective cofactors. 8. Pathways of biosynthesis of 5α-androst-16-en-3α- and 3β-ols, with the C19 3-oxo steroids as intermediates, are presented.