C-21- and 6-hydroxylation of progesterone by rabbit liver subcellular fractions

In vitro C-21-hydroxylation of [3H]progesterone (P) has been demonstrated for the first time with rabbit liver microsomes and mitochondria. Deoxycorticosterone (DOC) was rigorously characterized as a metabolite of both mitochondrial and microsomal metabolism, whereas 6alpha-hydroxy DOC and 6alpha-hydroxy P were only identified as microsomal metabolites. 6beta-Hydroxy metabolites were also detected but were of less quantitative significance. Formation of 6alpha-hydroxy P and 6alpha-hydroxy DOC increased steadily between 5 and 120 min of incubation with the microsomal fraction, whereas DOC increased up to 30 min of incubation and then declined. Maximal yield of DOC was 25.9 and 22.5 pmol/mg protein with the mitochondrial and microsomal fractions, respectively.