OXYGEN-SENSING BY ION CHANNELS AND THE REGULATION OF CELLULAR FUNCTIONS

From bacteria to mammals, ambient O-2 tension influences such diverse cellular functions as gene expression, secretion, contraction and the patterns of electrical activity. Some of the effects of O-2 are attrib uted to its interaction with various classes of voltage-dependent ion channels. In glomus cells of the carotid body, the differential proper ties of O-2-sensitive K+ and Ca2+ channels help us to understand the b asic features of O-2 chemoreception. Modifications of ion-channel acti vity in response to changes in the partial pressure of O-2 are also in volved in the adjustments of vascular tone to hypoxia as well as in th e response of chemoreceptors in pulmonary airways. Direct O-2-sensing by ion channels might also help to explain the alterations of brain fu nction by low O-2 tension. The O-2-sensitivity of ion-channel activity appears to be a broadly distributed phenomenon contributing to a wide variety of cellular responses to hypoxia.