The hepatic aquaporin 9 (AQP9) expression is regulated in response to castration and PPARα‐ agonist treatment

Abstract

It has previously been shown that male rats have higher hepatic expression of AQP9 than female rats (Nicchia et al, J Histochem Cytochem, 2001). The regulation of hepatic AQP9 has also been related to PPARα (Patsouris et al, J Clin Invest, 2004). This study aims to investigate the role of castration and PPARα–agonist (Wy 14643) administration in regulation of hepatic AQP9 protein expression in male rats. In castrated rats, immunoblotting showed a 1.7 fold increase in hepatic AQP9 (p < 0.01). This finding was confirmed by immunohistochemical analysis. Serum testosterone was decreased in the castrated group (p < 0.01), while serum insulin was 1.0 ± 0.3 and 1.9 ± 0.6 in castrated and controls, respectively, however this was not statistically significant and plasma glucose levels remained unchanged. In rats treated for 10 days with Wy 14643 (3 mg/kg/day), immunoblotting showed a 2.6‐fold decrease in the expression of hepatic AQP9 (p < 0.001). Immunohistochemical analysis revealed a marked decrease of AQP9 in the periportal zone, whereas AQP9 expressed in the perivenous zone appeared unchanged. There were no changes in serum insulin or glucose levels. We conclude that hepatic AQP9 protein expression increases in response to castration in male rats, whereas treatment with PPARα–agonist results in a marked decrease and redistribution of hepatic AQP9 protein.Supported by the Danish National Research Foundation