title: Cation transport systems in mitochondria: Na+ and K+ uniports and exchangers.
abstract: It is now well established that mitochondria contain three antiporters that transport monovalent cations. A latent, allosterically regulated K+/H+ antiport appears to serve as a cation-extruding device that helps maintain mitochondrial volume homeostasis. An apparently unregulated Na+/H+ antiport keeps matrix [Na+] low and the Na(+)-gradient equal to the H(+)-gradient. A Na+/Ca2+ antiport provides a Ca(2+)-extruding mechanism that permits the mitochondrion to regulate matrix [Ca2+] by balancing Ca2+ efflux against influx on the Ca(2+)-uniport. All three antiports have well-defined physiological roles and their molecular properties and regulatory features are now being determined. Mitochondria also contain monovalent cation uniports, such as the recently described ATP- and glibenclamide-sensitive K+ channel and ruthenium red-sensitive uniports for Na+ and K+. A physiological role of such uniports has not been established and their properties are just beginning to be defined.
authors.affiliation: Department of Medical Biochemistry, Ohio State University, Columbus 43210.
authors.forename: G P
authors.initials: GP
authors.lastname: Brierley
authors.forename: K
authors.initials: K
authors.lastname: Baysal
authors.forename: D W
authors.initials: DW
authors.lastname: Jung
mesh_terms: D000818:Animals; D002352:Carrier Proteins / Q000378:metabolism*; D002414:Cations, Monovalent / Q000378:metabolism; D008928:Mitochondria / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*
chemical_list: D002352:Carrier Proteins; D002414:Cations, Monovalent; D019831:Sodium-Calcium Exchanger; D017923:Sodium-Hydrogen Exchangers; D012964:Sodium; D011188:Potassium