Aquaporin-1 expression in canine peripheral erythrocytes and its relation to cell volume.

To evaluate the relationship between aquaporin-1 (AQP1) expression and the cell volume of red blood cells (RBCs), canine peripheral RBCs were separated according to specific gravity, and expression of the AQP1 protein on the membrane of RBCs was compared using anti-dog AQP1 polypeptide serum. Western blot analysis indicated that there was no significant difference in AQP1 expression between large and small cell fractions. In addition, the AQP1 expression of inherited high K/low Na RBCs which are known to be 20% larger than normal RBCs, was comparable to that of normal RBCs. These results suggest that AQP1, the major water channel in RBCs, does not determine the cell volume of peripheral canine RBCs.