Calcium-induced net potassium uptake of pig hearts in vivo.
To determine whether the catecholamine-induced myocardial potassium uptake could be mimicked by increasing extracellular and intracellular calcium concentrations in vivo, we measured changes in myocardial potassium balance in nine anaesthetized open-chest pigs with PVC-valinomycin electrodes in arterial and coronary sinus blood. CaCl2 infusion (200-400 mumol min-1) into the left coronary artery increased coronary sinus blood calcium concentration from 2.29 (2.19-2.42) to 4.63 (3.76-5.67) mmol l-1 (median, 95% confidence interval, P = 0.01) indicating a similar increment in myocardial extracellular calcium concentration. The contractility measure LV dP/dt increased 95 (76-147) %, indicating a substantial increment in intracellular calcium concentration. During the CaCl2 infusion coronary sinus potassium concentration declined to a nadir 0.12 (0.09-0.17) mmol l-1 below baseline (P = 0.008) whereas arterial concentration remained unchanged. Peak myocardial potassium uptake was 18 (7-32) mumol min-1 100 g-1 and occurred 150 (110-195) s after start of infusion. The response remained unaltered after adrenoceptor blockade by prazosin and propranolol. Prolonged CaCl2 infusion caused a net myocardial potassium loss which was accompanied by metabolic and haemodynamic indications of myocardial ischaemia. These findings are consistent with enhanced Na-K pump activity in the intact beating pig heart in response to increased extracellular and intracellular calcium concentrations.
Ellingsen
O
O
Institute for Experimental Medical Research, University of Oslo, Norway.
Aksnes
G
G
Ilebekk
A
A
D000818:Animals; D002118:Calcium / Q000097:blood; D002122:Calcium Chloride / Q000008:administration & dosage / Q000494:pharmacology*; D005260:Female; D006439:Hemodynamics; D007261:Infusions, Intra-Arterial; D008297:Male; D009200:Myocardial Contraction / Q000187:drug effects; D009206:Myocardium / Q000378:metabolism*; D011188:Potassium / Q000378:metabolism*; D000254:Sodium-Potassium-Exchanging ATPase / Q000187:drug effects; D013552:Swine
D000254:Sodium-Potassium-Exchanging ATPase; D002122:Calcium Chloride; D011188:Potassium; D002118:Calcium