Medroxyprogesterone acetate (MPA) enhances liver NADPH-generating enzyme activities in normal rats

The aim of the present study was to evaluate the effects of medroxyprogesterone acetate (MPA), an inducer of liver drug metabolism, on the ability of liver to generate NADPH, a reducing cofactor for drug oxidation reactions in normal rats and to compare these results with those obtained in rats receiving phenobarbital (PB), a well known inducer of liver drug metabolism. The results showed that: 1. Administration of MPA (100 mg/kg body wt) for a week increased liver wt and NADPH cytochrome P-450 reductase activity, suggesting that the compound induced liver drug metabolism. 2. The regimen also increased the activities of two NADPH generating enzymes, isocitrate dehydrogenase and malic enzyme, suggesting that MPA enhanced the capacity of normal liver tissue to produce NADPH. 3. Phenobarbital treatment increased the activities of three NADPH generating enzymes, glucose-6-phosphate dehydrogenase, 6-phosphogluconate dehydrogenase and malic enzyme, suggesting that MPA and PB differ in their effects on the liver NADPH-producing system.