Inhibition of potassium-induced contracture of the isolated rat aorta by amiloride.
Potassium contractures of helically cut strips of rat aorta were recorded isometrically. Contractures induced by KCl 40 mmol/l were decreased dose-dependently by amiloride (1.7 X 10(-5) to 1.4 X 10(-4) mol/l) added to the bath 10 min before the depolarization. Ouabain (10(-3) mol/l) antagonized this effect. Contractures induced by using, instead of normal Krebs solution, a solution in which potassium was replaced by sodium (Krebs potassium) were also decreased dose-dependently by amiloride, but the slope of the linear log dose-effect curve line was steeper. When arteries were incubated in a solution deprived of sodium and calcium (isotonicity maintained by choline), the intensity of consecutive contractures by Krebs potassium decreased progressively. Incubation in a normal Krebs solution restored the normal contractures; amiloride added at the same time prevented this restoration. These findings are in agreement with the assumption that sodium-calcium exchange plays an important part in the contracture of vascular smooth muscles.
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001011:Aorta / Q000187:drug effects; D002118:Calcium / Q000502:physiology; D066298:In Vitro Techniques; D008297:Male; D009119:Muscle Contraction / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D010042:Ouabain / Q000494:pharmacology; D011188:Potassium / Q000037:antagonists & inhibitors*; D011189:Potassium Chloride / Q000037:antagonists & inhibitors; D011719:Pyrazines / Q000494:pharmacology*; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000502:physiology
D011719:Pyrazines; D010042:Ouabain; D011189:Potassium Chloride; D000584:Amiloride; D012964:Sodium; D011188:Potassium; D002118:Calcium