Vascular sodium pump activity kinetics in early and advanced stages of deoxycorticosterone-salt hypertension in rats.
We determined the kinetic properties--the maximal velocity, Vmax, and the half-maximal activating concentration of K+, km values--of the vascular sodium pump in rats 6, 28, and 50 days after deoxycorticosterone and sodium chloride (DOC-salt) or vehicle treatment. Tail arteries from six or eight rats from each treatment group were pooled, and Na-pump activity was measured in a Krebs medium containing varying K+ (plus 86Rb+) concentrations (0.25-10 mM). Na-pump activity was plotted as a function of [K + 86Rb]. Data were fit to a two-site model to calculate Vmax and km values. Systolic blood pressures were normal after 6 days but high after 28 and 50 days of DOC-salt treatment. No difference in kinetic parameters existed between the treatment and control groups 6 and 50 days after DOC-salt treatment. After 28 days, Vmax was significantly elevated compared with controls; km was not affected. Thus, stimulation of the vascular Na-pump during established hypertension is due to an increase in the maximal velocity of ouabain-sensitive uptake of K+.
Songu-Mize
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Department of Pharmacology, College of Medicine, University of Tennessee, Memphis 38163.
D000818:Animals; D001158:Arteries / Q000378:metabolism*; D001835:Body Weight; D003900:Desoxycorticosterone / Q000494:pharmacology*; D006973:Hypertension / Q000139:chemically induced / Q000378:metabolism*; D007700:Kinetics; D008297:Male; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism; D012965:Sodium Chloride / Q000494:pharmacology; D000254:Sodium-Potassium-Exchanging ATPase / Q000502:physiology*
D003900:Desoxycorticosterone; D012965:Sodium Chloride; D010042:Ouabain; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium