Immunolocalization of aquaporin-4 in the brain, kidney, skeletal muscle, and gastro-intestinal tract of chicken.

Aquaporin-4 (AQP4), a member of the water channel family, has high water permeability and multi-functional potentiality. Although an avian AQP4 homolog has recently been identified, its overall localization is still largely unknown. This study demonstrates the presence of AQP4 in several organs of chicken by using a specific chicken AQP4 antibody. Western blot analysis has revealed two bands of chicken AQP4 (30 and 32 kDa) in the brain, proventriculus, pectoral muscle, kidney, and ureter. The brain is the primary expression site of AQP4 in chicken. Immunohistochemical analysis of the brain has shown the highest AQP4 immunoreactivity around the cerebral ventricles, blood vessels, and the Purkinje cells. In peripheral organs, AQP4-immunoreactive elements have been observed in the ureter, glandular cells of the proventriculus, sarcolemma of the pectoral muscle, and the epithelium of the ceca and the rectum. Moreover, a heavily stained network of AQP4-immunoreactive fibers has been detected within the enteric plexuses.