Myocardial potassium uptake during alpha- and beta-adrenoceptor stimulation.
The changes in myocardial K+ balance during alpha- and beta-adrenoceptor stimulation were compared in 10 anesthetized open-chest pigs by intracoronary isoproterenol and phenylephrine infusions. K+ concentration was continuously recorded by polyvinyl chloride catheter-valinomycin minielectrodes in arterial and coronary sinus blood. The arterial-coronary sinus difference and accumulated myocardial K+ uptake were calculated after computerized data sampling. Isoproterenol (2.5 nmol/min ic) reduced coronary sinus K+ transiently to a nadir of 0.37 (0.23-0.53) mM (median and 95% confidence interval) below control. The accumulated K+ uptake amounted to 139 (63-215) mumol/100 g. After beta-blockade by propranolol, phenylephrine (100 nmol/min ic) induced a transient coronary sinus K+ lowering of 0.16 (0.13-0.21) mM and an accumulated K+ uptake of 30 (20-41) mumol/100 g, both values less than those of isoproterenol (P less than 0.001). Myocardial contractility increased only during isoproterenol infusion, arterial blood pressure rose slightly by phenylephrine, but changes in myocardial O2 extraction and lactate uptake did not indicate cardiac ischemia. We conclude that both alpha- and beta-adrenoceptor stimulation induce a myocardial K+ uptake presumably due to increased Na-K pump activity, the latter more efficiently.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D001330:Electronic Data Processing; D005260:Female; D005947:Glucose / Q000378:metabolism; D006439:Hemodynamics; D007545:Isoproterenol / Q000494:pharmacology; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010101:Oxygen Consumption; D011188:Potassium / Q000493:pharmacokinetics*; D013552:Swine
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D007773:Lactates; D019344:Lactic Acid; D005947:Glucose; D007545:Isoproterenol; D011188:Potassium