Sensing Tension

T he epithelial sodium (Na ) channel (ENaC) plays a critical role in blood pressure regulation by controlling renal salt and water reabsorption. Channel overactivity can lead to severe hypertension and underactivity to salt wasting and hypotension. In addition to their role in salt/water homeostasis, recent studies suggest that ENaC proteins, and their relatives, the acid-sensing ion channel (ASIC) proteins, may play more ubiquitous roles in cardiovascular regulation than considered previously. Recent evidence suggests that ENaC/ASIC proteins may act as mechanosensors and chemosensors in the cardiovascular system. ENaC/ASIC proteins are expressed in mechanosensing and chemosensing tissues, such as vascular smooth muscle cells (VSMCs), carotid body glomus cells, and sensory neurons innervating arterial baroreceptors, heart, and skeletal muscle. Disruption of the ENaC/ ASIC channels alters myogenic constriction, arterial chemoreceptor and baroreceptor responses, and acid-induced responses in heart and skeletal muscle. This brief review summarizes the evidence supporting a role for ENaC and ASIC proteins in diverse systems of cardiovascular mechanosensing and chemosensing. Together, these studies suggest that ENaC/ASIC proteins contribute to cardiovascular homeostasis by mediating neural and local regulatory mechanisms.