Urinary concentration of aquaporin-2 water channel protein at different stages of chronic heart failure rats

AIM: To study urinary concentration of aquaporin-2 water channel protein(AQP2) at different stages of chronic heart failure(CHF) rats and its relation to hyponatremia. METHODS: Male Sprague-Dawley rats(200~250 g) underwent either a left coronary artery ligation (a model of CHF) or a sham-operation. At different stage after surgery, urinary AQP2 concentration was measured by Western blot. 24-hours urine volume, serum sodium and urine osmolality were measured at the same time. RESULTS: There were two peaks of urinary excretion of AQP2 in severe heart failure rats model: one was the third day after operation, the other was the 9th week. Serum sodium and urine osmolality were significantly different in CHF rats as compared with sham-operated rats. Seven weeks after surgery, urinary AQP2 concentration was increased significantly insevere CHF rats compared with the mild ones and the control ones(365%±103% vs 179%±81% and 99%±48%, P＜0.01).CONCLUSION: The variation of urinary AQP2 excretion at different stages after ligation showed that the expression of AQP2 gene was increased obviously in CHF rats, and its expression level was higher as the heart failure became more severe.This is the important reason of heart failure with hyponatremia.