Influence of chronic alterations of salt intake and aging on the kinetic of red cell Na+ and K+ transport in Sprague-Dawley rats.
The kinetics of Na+ and K+ (Rb)+ transport mediated by the Na(+)-K+ pump and Na(+)-K+ cotransport system (assessed as a function of Rb+o and Na+i) as well as the magnitude of cation leaks were determined in red cells of young male rats subjected to chronic salt deprivation or salt loading (0.1% and 8% NaCl diet). These salt intake alterations induced moderate kinetic changes of the Na(+)-K+ pump which did not result in significant changes of ouabain-sensitive (OS) Rb+ uptake or Na+ net extrusion at in vivo Na+i and K+o concentrations because a decreased affinity for Na+i in salt-loaded animals was compensated by an increased maximal transport rate. High furosemide-sensitive (FS) Rb+ uptake in red cells of salt-deprived rats was caused by an increase of both the maximal transport rate and the affinity for Rb+o. Cation leaks were also higher in salt-deprived than in salt-loaded rats. In three age groups of rats fed a 1% NaCl diet FS Rb+ uptake (but not FS Na+ net uptake) rose with age due to an increasing maximal transport rate whereas the affinity of the cotransport system for Rbo+ did not change. The age-dependent changes in the kinetics of the Na(+)-K+ pump resulted in a slight decrease of OS Rb+ uptake with age that was not paralleled by corresponding Na+ net extrusion. No major age-related changes of cation leaks were found. Thus some intrinsic properties of red cell transport systems can be altered by salt intake and aging.
Zicha
J
J
Institute of Physiology, Czechoslovak Academy of Sciences, Prague.
Duhm
J
J
D000375:Aging / Q000097:blood*; D000818:Animals; D001692:Biological Transport; D001794:Blood Pressure; D002352:Carrier Proteins / Q000378:metabolism; D004912:Erythrocytes / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000097:blood / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000097:blood / Q000378:metabolism*; D012982:Sodium, Dietary / Q000008:administration & dosage*; D028021:Sodium-Potassium-Chloride Symporters
D002352:Carrier Proteins; D012982:Sodium, Dietary; D028021:Sodium-Potassium-Chloride Symporters; D010042:Ouabain; D005665:Furosemide; D012964:Sodium; D011188:Potassium