title: Membrane transport of sodium ions in erythrocytes of the American black bear, Ursus americanus.
abstract: 1. Membrane transport of Na ions was investigated in red blood cells of bears by methods of measurement of unidirectional isotopic fluxes. 2. Like red blood cells of dogs, bear red cells contain a high Na concentration and low concentrations of K and ATP. 3. As in dog red cells, Na efflux from bear cells was not inhibited by ouabain but was activated by the presence of Ca in the medium, possibly indicating the presence of a Na-Ca exchange mechanism. 4. ATP depletion of cells was accelerated by Ca in the medium, consistent with the presence of a strong ATP-dependent Ca pump. 5. As in other carnivore red cells, Na influx into bear cells was strongly activated by shrinkage and inhibited by swelling. Shrinkage-activated influx was blocked by amiloride. 6. Amiloride-sensitive influx was activated by cytoplasmic Ca and also correlated with the presence of a Na-dependent, amiloride-sensitive H loss. 7. Amiloride-sensitive Na influx exhibited a strong seasonal cycle with a minimum in the middle of the hibernation period, suggesting a possible avenue of cellular energy conservation.
authors.affiliation: Department of Physiology and Biophysics, University of Illinois, Urbana 61801.
authors.forename: J S
authors.initials: JS
authors.lastname: Willis
authors.forename: R A
authors.initials: RA
authors.lastname: Nelson
authors.forename: C
authors.initials: C
authors.lastname: Gordon
authors.forename: P
authors.initials: P
authors.lastname: Vilaro
authors.forename: Z H
authors.initials: ZH
authors.lastname: Zhao
mesh_terms: D000818:Animals; D001692:Biological Transport / Q000502:physiology; D002335:Carnivora / Q000097:blood*; D004910:Erythrocyte Membrane / Q000378:metabolism*; D005260:Female; D006605:Hibernation / Q000502:physiology; D006863:Hydrogen-Ion Concentration; D008297:Male; D012621:Seasons; D012964:Sodium / Q000097:blood*; D001503:Ursidae / Q000097:blood*
chemical_list: D012964:Sodium