The genetic control of the activities of microsomal steroidogenic enzymes in Leydig cells of inbred strains of mice

Pour activities of key microsomal steroidogenjc enzymes (3 beta-hyaroxyster oid dehydrogenase-isomerase, microsomal cytochrome P450(17 beta), and 17-ke tosteroid reductase) were compared in Leydig cells of six inbred strains of mice: A/He, CBA/Lac, C57BL/6J, DD, YT, and PT. The activities of the enzym es were found to vary considerably from one strain to another, depending on the genotype, Analysis of testosterone biosynthesis revealed a decreased a ctivity of 17-ketosteroid reductase as compared to the activities of other microsomal steroidogenic enzymes, The metabolism of pregnenolone and proges terone demonstrated features dependent on the genotype and caused by genoty pic differences in the activities of microsomal steroidogenic enzymes. Thes e activities demonstrated a correlative interstrain variation indicative of their coordinated genetic control. The correlative variation may be relate d to a major gene effect on the activities of microsomal steroidogenic enzy mes.