The mechanisms of action of noradrenaline on ouabain-sensitive rubidium uptake in guinea-pig myocardium.
The mechanism by which noradrenaline stimulates ouabain-sensitive rubidium uptake in guinea-pig myocardial tissue has been studied. The stimulatory action of low concentrations of noradrenaline was reversed by high doses of propranolol (10(-5) mol/l) in atrial tissue, but was not reversed by alpha- or beta-, or combined alpha- and beta- adrenoceptor antagonists in ventricular tissue. Rubidium uptake was also found to increase with increasing extracellular potassium concentration [( K]o). The percentage values of stimulation by noradrenaline decreased with increasing [K]o. Noradrenaline had no effect on the rate of ATP splitting by an isolated membrane preparation of Na,K-ATPase. It is proposed that noradrenaline stimulates active cation transport by either (a) an effect secondary to increased passive efflux of K ions, or (b) an action at a novel adrenergic receptor, distinct from the ATPase enzyme itself.
D000818:Animals; D001262:Atenolol / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D006168:Guinea Pigs; D006321:Heart / Q000187:drug effects; D066298:In Vitro Techniques; D009206:Myocardium / Q000201:enzymology / Q000378:metabolism*; D009638:Norepinephrine / Q000494:pharmacology*; D010042:Ouabain / Q000494:pharmacology; D010646:Phentolamine / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism; D011433:Propranolol / Q000494:pharmacology; D012413:Rubidium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013268:Stimulation, Chemical
D001262:Atenolol; D010042:Ouabain; D011433:Propranolol; D000254:Sodium-Potassium-Exchanging ATPase; D012413:Rubidium; D011188:Potassium; D009638:Norepinephrine; D010646:Phentolamine