Expression of multidrug resistance-associated protein 2 in small intestinefrom pregnant and postpartum rats

We analyzed the expression of multidrug resistance-associated protein 2 (mr p2) in the small intestine of control female rats and in rats during late p regnancy (19-20 days of pregnancy) and lactation (2-4, 10-14, and 21 days a fter delivery). Western blot analysis was performed on brush-border membran es prepared from different regions of the small intestine. Expression of mr p2 was maximal in the proximal segments for all experimental groups, was pr eserved in pregnant rats, and increased by 100% in postpartum rats by late lactation with respect to control animals. Northern blot analysis of mrp2 m RNA revealed a positive correlation with protein levels. Transport of S-glu tathione-dinitrophenol (DNP-SG) from the intestinal cell to the lumen was a nalyzed in the everted intestinal sac model. Secretion of DNP-SG was not al tered in pregnant rats but increased in lactating animals by late lactation . Intestinal mrp2 mRNA, protein, and transport activity are increased in la ctating rats, suggesting that this may represent an adaptive mechanism to m inimize the toxicity of dietary xenobiotics in response to increased postpa rtum food consumption.