Strain-, sex- and species-related differences of acetohexamide reductase and 20 beta-hydroxysteroid dehydrogenase activities in liver microsomes of experimental animals

We examined physiological and genetic factors affecting acetohexamide reduc tase (AHR) and 20 beta -hydroxysteroid dehydrogenase (20 beta -HSD) activit ies in liver microsomes of experimental animals. Pronounced strain-related differences were found in both activities of AHR and 20 beta -HSD present i n liver microsomes of male rats. Among rat strains tested in this study, ev en though a Wistar-Imamichi (WIM) rat strain was taken to lack AHR activity , it exhibited a significant 20 beta -HSD activity. These findings appeared to be in conflict with our conclusion reported so far, which AHR and 20 be ta -HSD present in liver microsomes of male rats are identical enzymes. Thu s the reason for this discrepancy was discussed. Furthermore, AHR and 20 be ta -HSD activities were little or not observed in liver microsomes of femal e rats or male experimental animals other than the rat, indicating the exis tence of sex- and species-related differences in these two enzyme activitie s.