CIRCANNUAL VARIATION AND GENETIC-REGULATION OF HEPATIC TESTOSTERONE HYDROXYLASE-ACTIVITIES IN INBRED STRAINS OF MICE

Hydroxylation of testosterone by hepatic microsomes at positions 6α, 6β, 7α, 15α, and 16α has been studied in C57BL/6J, 129/J, and A/J mice. Differences in hydroxylase activities between the C57BL/6J and A/J strains and between the C57BL/6J and 129/J strains were investigated using standard genetic breeding protocols. In the C57BL/6J × A/J line, 6α- and 7α-hydroxylase activity appeared to be under polygenic control in both sexes, as did 15α-hydroxylase activity in females. The lack of 16α-hydroxylase activity observed in 129/J females behaved as a recessive, autosomal, single locus, sex-limited trait. In several instances, the level of hydroxylase activity at one position appeared to be affected by the level of hydroxylase activity at a second position; however, no clear-cut pattern was discerned. Over a period of a year, a remarkable cycle in total hydroxylase activity for all mice was observed; the average activity was greatest in December and least in April. © 1979 by The Endocrine Society.