Biochemical and expression studies on Aquaporin 9 (AQP9) in wild and AQP9 knockout mice

The objective of this study was to determine the cellular and subcellular localization of AQP9 in different organs of wild-type (AQP9(+/+)) and AQP9 knockout mice (AQP9(-/-)) by immunohistochemistry (IHC), immunofluorescence (IF) and RT-PCR, as well as some biochemical evaluation. Twenty wild and homozygous AQP9 KO-mice (C57 BL/6J) were used. Both AQP9(+/+) and AQP9(-/-) were randomly assigned to 4 Subgroups based on sex type. IHC analyses revealed AQP9 specific labeling in the hepatocytes, kidney, spleen and epididymis of wild type mice (AQP9(+/+)), but a complete absence of labeling in AQP9(-/-) mice. In the liver, labeling was strongest at the sinusoidal surface, and there was little intracellular labeling. AQP9 expression was found to be sex-linked. In the liver of females, the expression of AQP9 was mostly confined to perivascular hepatocytes, whereas males showed more homogeneous hepatocyte staining. Confocal immunofluorescence confirmed the localization of AQP9 immunostaining on the basolateral plasma membrane of hepatocytes. Compared with the control mice, serum levels of glycerol and triglycerides were significantly (P<0.05) increased, in association with hypoglycemia in the AQP9(-/-) mice, whereas the total cholesterol, urea, alanine aminotransferase, and alkaline phosphatase were not statistically different.