Effect of goreisan on urinary concentrating ability and expression of aquaporin-2 in 5/6 nephrectomized rats

The purpose of this study was to investigate the effect of goreisan, a Kampo (traditional Chinese herbal medicine) formula, on the urinary concentrating ability and the expression of aquaporin 1-3 (AQP1-3) in 5/6 nephrectomized (5/6Nx) rats. Two weeks after 5/6 nephrectomy, the rats were divided into three groups: 0.5% goreisan-treated, 1% goreisan-treated and controls. Additionally, each 5/6Nx group and sham-operated group (sham) was divided into 4- and 8 week-observed groups. The serum potassium concentration in the 1% goreisan-treated group was significantly increased compared with that in the 5/6Nx groups. The remnant kidney weight and urinary protein excretion of 1% goreisan-treatment for 8 weeks were significantly decreased compared with those of controls. The urine osmolality of 1% goreisan treatment for 8 weeks was significantly higher than that of controls. AQP2 expression in the inner medulla, outer medulla and cortex were not decreased by 5/6Nx, but expression in all areas was decreased by goreisan. Furthermore, the expression of AQP3 in the goreisan-treated group in the cortex was significantly increased compared with that in the 5/6Nx groups. The changes in urinary osmolality and the decrease in AQP2 and increase in AQP3 expression by goreisan-treatment in 5/6Nx rats suggest that AQPs expression is associated with the effects of goreisan on modulation of water balance.