Impact of 17-alpha-hydroxyprogesterone caproate on cytochrome P450s in primary cultures of human hepatocytes.

The aim of this study was to examine the effects of 17-alpha-hydroxyprogesterone caproate (17OHP-C) on the activity and expression of several common hepatic cytochrome P450 (CYP) enzymes. Primary human hepatocytes were pretreated with vehicle or 17OHP-C (0.1 and 1 μmol/L) for 72 hours, then incubated for 1 hour with a cocktail of CYP substrates. The activity of various CYP enzymes was determined by measuring the formation of the metabolites of specific CYP substrates, using liquid chromatography-tandem mass spectrometry. The messenger RNA expression of various CYP enzymes was determined by real-time polymerase chain reaction. In primary cultures of human hepatocytes, 17OHP-C minimally altered the activity or messenger RNA levels of CYP1A2, CYP2C9, CYP2D6, and CYP3A. However, 17OHP-C at 1 μmol/L increased CYP2C19 activity by 2.8-fold (P < .01) and CYP2C19 expression by 2.4-fold (P < .001), compared with vehicle-treated cells. A strong positive correlation between activity and expression of CYP2C19 was also observed (r = 0.9, P < .001). The activity and expression of hepatic CYP2C19 was significantly increased by 17OHP-C in primary cultures of human hepatocytes. This suggests that exposure to medications that are metabolized by CYP2C19 may be decreased in pregnant patients receiving 17OHP-C. Metabolism of substrates of CYP1A2, CYP2C9, CYP2D6, and CYP3A are not expected to be altered in patients receiving 17OHP-C.