Sodium pump activity and calcium relaxation in vascular smooth muscle of deoxycorticosterone acetate-salt rats.
The Na+-K+ pump activity was determined in femoral arterial smooth muscle from deoxycorticosterone acetate (DOCA)-salt hypertensive rats using potassium relaxation and ouabain-sensitive 86Rb uptake as indices. The membrane-stabilizing effect of calcium and its relation to Na+-K+ pump activity also were examined. Femoral arteries from DOCA-salt rats exhibited a greater relaxation in response to potassium addition after contraction with norepinephrine in a low potassium (0.6 mM) Krebs solution. The concentration of potassium required to produce a 50% relaxation was significantly less in DOCA-salt rats. Ouabain-sensitive 86Rb uptake was significantly greater at 3, 10, and 20 minutes of 86Rb incubation in femoral arteries from DOCA-salt rats. Linear regression analysis revealed a significant correlation between the uptake of 86Rb and time of incubation in both control and DOCA-salt rats. A significant difference in the slopes of the regression lines showed that the rate of uptake was greater in DOCA-salt rats. No difference was observed in ouabain-insensitive 86Rb uptake. A dose-dependent relaxation in response to increasing concentrations of calcium following contraction to norepinephrine was observed in femoral arteries from control and DOCA-salt rats. The relaxation was directly dependent on the level of extracellular potassium and was blocked by ouabain. Femoral arteries from DOCA-salt rats relaxed to a significantly greater extent in response to calcium at each level of potassium when compared with controls. These results provide further evidence for an increase in Na+-K+ pump activity in vascular smooth muscle from DOCA-salt hypertensive rats.(ABSTRACT TRUNCATED AT 250 WORDS)
D000818:Animals; D002118:Calcium / Q000502:physiology*; D002122:Calcium Chloride / Q000494:pharmacology; D005263:Femoral Artery; D006973:Hypertension / Q000378:metabolism*; D007473:Ion Channels / Q000378:metabolism*; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D011189:Potassium Chloride / Q000494:pharmacology; D011868:Radioisotopes / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
D007473:Ion Channels; D011868:Radioisotopes; D011189:Potassium Chloride; D012964:Sodium; D002122:Calcium Chloride; D012413:Rubidium; D011188:Potassium; D002118:Calcium; D009638:Norepinephrine