Changes in maternal liver Cyp2c and Cyp2d expression and activity during rat pregnancy

Abstract

During human pregnancy, CYP2C9, CYP2C19, and CYP2D6 activities are altered. The aim of the current study was to determine if this phenomenon can be replicated in the rat, and to evaluate the mechanisms that contribute to the changes in Cyp2c and Cyp2d activity during pregnancy. The intrinsic clearance of dextromethorphan O-demethylation, a measure of Cyp2d2 activity, was decreased 80% at both days 9 and 19 of gestation when compared to non-pregnant controls. The decreased intrinsic clearance was a result of both decreased V(max) and increased K(m)-values at both days of gestation. Quantitative RT-PCR revealed that transcripts of Cyp2d2 and Cyp2d4 were significantly decreased at day 19 of pregnancy (p<0.05) when compared to day 9 and non-pregnant controls. The decrease in Cyp2d mRNA levels correlated with a decrease in several nuclear receptor mRNA levels (RARalpha, RXRalpha, HNF1 and HNF3beta) but not with the mRNA levels of nuclear receptors usually associated with regulation of P450 enzymes (PXR, CAR and HNF4alpha). In contrast, Cyp2c12 and Cyp2c6 transcription and protein expression were not significantly altered during rat pregnancy although the intrinsic clearance of Cyp2c6 mediated diclofenac 4'-hydroxylation was increased 2-fold on day 19 of gestation when compared to non-pregnant controls. The increase in intrinsic clearance was due to a decrease in the K(m)-value for 4'-hydroxydiclofenac formation. These data show that pregnancy significantly alters the expression and activity of drug metabolizing enzymes in an enzyme and gestational stage specific manner. These changes are likely to have toxicological and therapeutic implications.

Pregnancy Decreases Rat CYP1A2 Activity and Expression

“…This result is noteworthy because the decreased CYP1A2 activity observed in the rat is in close agreement with the 45 and 65% decrease in caffeine oral clearance during mid-and late pregnancy (Tracy et al, 2005). In contrast to the gestational stage-specific changes in mRNA and protein of CYP2D and CYP2C enzymes during rat pregnancy (Dickmann et al, 2008), no significant differences were observed between gestational stages in CYP1A2 activity or expression. This finding again highlights the fact that the effects of pregnancy are specific for a given P450 enzyme, and the mechanisms that result in altered P450 expression and activity during pregnancy vary between isoforms.…”

“…Protein levels of CYP1A2 were determined by Western blotting using 10 g of liver microsomal protein from each animal as described previously (Dickmann et al, 2008). Membranes were probed with sheep anti-rat CYP1A2 (1:6000 dilution; Research Diagnostics, Flanders, NJ) and mouse anti-␤-actin (1:4000 dilution; Sigma-Aldrich) primary antibodies in Odyssey blocking solution (LI-COR Biosciences, Lincoln, NE) with 0.1% Tween 20, rinsed, and incubated with IRDye 700DX donkey anti-sheep (1:3000) and IRDye 800CW donkey anti-mouse (1:5000) secondary antibodies (Rockland Immunochemicals, Gilbertsville, PA).…”

“…Total liver RNA was isolated, quantified, and reverse transcribed to cDNA as described previously (Dickmann et al, 2008). CYP1A2, ␤2M, 18-S-Vic, and GusB transcripts were measured using commercially available TaqMan real-time polymerase chain reaction (PCR) primers and probes with PCR Master Mix on a StepOnePlus Real-Time PCR instrument (Applied Biosystems, Foster City, CA).…”

“…In the mouse, Cyp3a activity and protein expression increased during pregnancy (Mathias et al, 2006;Zhang et al, 2008), whereas in pregnant rats, CYP2D2 activity and mRNA decreased and CYP2C was unchanged (Dickmann et al, 2008). After oral administration to pregnant rats, the area under the plasma concentration time curve of caffeine was not different from that for nonpregnant rats, but the area under the plasma concentration time curve of theobromine and theophylline (formed by rat CYP1A2) decreased, suggesting reduced CYP1A2 activity (Abdi et al, 1993).…”

Alteration of the Expression of Pesticide-Metabolizing Enzymes in Pregnant Mice: Potential Role in the Increased Vulnerability of the Developing Brain

“…Recent studies investigated changes in rodent cytochrome P450 (Cyp) isoforms during pregnancy in mice Koh et al, 2011) and rats (He et al, 2005;Dickmann et al, 2008). However, data are lacking for some important Cyp isoforms involved in pesticide metabolism, and the regulation of hepatic Ces or Pon1 levels during pregnancy is not known.…”