Expression Of Aquaporin-8 In The Hepatocytes Of Pregnant Rats With Intrahepatic Cholestasis

Objective: Intrahepatic cholestasis of pregnancy(ICP) is a complication specifically occurred in pregnancy.The etiology has not been determined. Researches have been suggested that rats hepatocytes AQP8 contribute to osmotic water transport during canalular bile secretion. Our experiments try to investigate the alteration on the expression levels of protein and messenger RNA(mRNA) of AQP8 in the hepatocytes of pregnant rats with intrahepatic cholestasis induced by ethinylestradiol. To explore the significance of AQP8 in the pathogenesis of intrahepatic cholestasis of pregnancy(ICP).Methods: A total number of 20 15-day pregnant rats were randomly divided into two groups:control group and ICP group. In ICP group,rats were subcutaneously injected with ethinylestradiol(EE) (2.5mg.kg-1.d-1 )for 5 days to make the model.In control group, rats received subcutaneous injection of appropriate volume of propylene glycol(PG) for 5 days .The levels of serum aminotrartsferases (ALT),aspartate transamlnase (AST),serum total bile salt (TBA) were measured before and 5 days after the treatment respectively. The activities of Na+-K+-ATPase of the hepatocytes were examined in two groups by colorimetric method, the protein expression and subcellular localization of AQP8 in the hepatocytes of pregnant rats were detected using immunohistochemical methods. The expression of AQP8 mRNA in the hepatocytes was assayed by RT-PCR method.Results: In ICP group, ALT,AST,TBA of 5 days after the treatment significantly increased compared with before(P<0.05), but control group showed no signs of significant change(P>0.05) , The activity of Na+-K+-ATPase in ICP group was 0.61±0.12, decreased significantly than in control group(0.85±0.07) (P<0.05). The model of ICP pregnant rats was made successfully. AQP8 protein and mRNA were found in the hepatocytes,and AQP8 protein level in ICP group was 10.80±2.40,significantly decreased than in control group(17.14±2.24) (P<0.05). AQP8 mRNA level in ICP group (1.07±0.11) was significantly higher than in control group (0.80±0.11 )(P<0.05).Conclusions: (1)The study demonstrates the exprssion of AQP8 protein and mRNA in pregnant rats hepatocytes. The protein expression of AQP8 in the hepatocytes of pregnant rats was mainly localized in intracecellular vesicles. The AQP8 contribute to osmotic water transport during canalular bile secretion in rats Hepatocytes. (2) AQP8 protein expression was down-regulated, AQP8 mRNA expression was up-regulated in the hepatocytes of pregnant rats with intrahepatic cholestasis, which contribute to bile secretory dysfunction of intrahepatic cholestasis of pregnancy (ICP).Down-regulated of AQP8 protein and up-regulated of AQP8 mRNA expression in the hepatocytes of ICP may be important to lead to the pathogenesis of intrahepatic cholestasis of pregnancy (ICP).