Expression of aquaporin 1 in human cardiac and skeletal muscle.

Aquaporins (AQPs) are a family of water channel proteins that assist in maintenance of the cellular osmotic environment and whole body fluid balance. Specialized organ-specific AQPs are important in physiologic and pathologic processes but little is known about AQPs in the human heart. AQP1 has been identified in rodent heart. We investigated the presence and localization of AQP1 in human heart and skeletal muscle using immunohistochemistry and confocal microscopy, western blot and reverse transcriptase-polymerase chain reaction. There was abundant AQP1 present in both cardiac and skeletal muscle. Immunohistochemistry revealed co-localization of AQP1 with vinculin, a t-tubule marker, and caveolin-3. No novel sequences bearing an NPA box motif common to other AQPs were identified in human heart using degenerative PCR analysis. We conclude that AQP1 is present in the human heart. AQP1 co-localizes with t-tubular and caveolar proteins. Cardiac AQPs may have a role during osmotic stresses including ischemia/reperfusion and cardiopulmonary bypass.