title: [Na+/H+- and Na+/Na+-countertransport in human, rabbit, and rat erythrocytes: evidence for the existence of two independent ion-transporting systems].
abstract: The activity and regulatory features of the Na+/H(+)- and Na+/Na(+)-exchange were studied in human, rabbit and rat red blood cells. No basal activity of the Na+/H(+)-exchange (the amyloride-inhibited component of the 22Na+ influx) in erythrocytes of these species was observed. The rate of 22Na+ influx increased rapidly when the experiments were carried out on acid-loaded cells in an alkaline (pH0 = 8.0) incubation medium (delta mu H(+)-induced Na+/H(+)-exchange). The ratio of delta mu H(+)-induced Na+/H(+)-exchange activities in human, rabbit and rat red blood cells was 1.0 : 1.1 : 2.3, respectively, whereas that of the Na+/Na(+)-exchange activities (the phloretin-inhibited component of the 22Na+ influx) in erythrocytes of these species was 1.0 : 4.6 : 0.2. The osmotic shrinkage of rat and rabbit erythrocytes led to the stimulation of the Na+/H(+)- (but not Na+/Na+) exchange. Amyloride (1 mM) inhibited the shrinkage-induced 22Na+ entry as well as the delta mu H(+)-induced 22Na+ entry--by 95 and 10-20%, respectively. Heat treatment (10 min, 49-51 degrees C), disturbing the membrane cytoskeleton suppressed both the shrinkage-induced activation and the delta mu H(+)-induced activation of the Na+/H(+)-exchange. The data obtained indicate that the both transport systems are mediated by two distinct transport carriers. It may be suggested that the delta mu H(+)-induced Na+/H(+)-exchange, on the one hand, and the shrinkage-induced Na+/H(+)-exchange, on the other, are mediated by two different Na+/H(+)-exchanger subtypes.
authors.forename: S N
authors.initials: SN
authors.lastname: Orlov
authors.forename: S R
authors.initials: SR
authors.lastname: Kuznetsov
authors.forename: I A
authors.initials: IA
authors.lastname: Kolosova
authors.forename: V L
authors.initials: VL
authors.lastname: Makarov
mesh_terms: D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D004910:Erythrocyte Membrane / Q000187:drug effects / Q000378:metabolism*; D005260:Female; D006801:Humans; D017136:Ion Transport; D007700:Kinetics; D009995:Osmosis; D011817:Rabbits; D051381:Rats; D017208:Rats, Wistar; D017923:Sodium-Hydrogen Exchangers / Q000378:metabolism*; D013045:Species Specificity
chemical_list: D017923:Sodium-Hydrogen Exchangers; D000584:Amiloride
vernacular_title: Na+/H+- i Na+/Na+-protivotransport v éritrotsitakh cheloveka, krolika,i krysy: dokaztel'stva sushestvovaniia dvukh nezavisimykh ion-transportiruiushchikh sistem.