title: Myocardial K+ repletion and rise in contractility after brief ischemic periods in the pig.
abstract: Potassium loss from the myocardium during brief ischemic periods is well documented, but whether intrinsic myocardial mechanisms restore this loss during reperfusion is unclear. To address this question, we established a shunt from the coronary sinus to the right atrium in seven open-chest pigs. Shunt flow and arterial and coronary sinus potassium concentrations were measured continuously in order to determine myocardial potassium balance. Thirty, 60 and 120 s occlusions of the mid-LAD coronary artery were repeated four times each at 10 min intervals with reproducible metabolic and hemodynamic responses. A myocardial K+ reuptake amounting to 51 to 77% of K+ release during ischemia occurred between 20 and 140 s of reperfusion. The maximal rate of K+ reuptake was 1.4 (0.7 to 3.6), (median and 95% confidence interval), 4.3 (2.5 to 9.6) and 7.3 (4.9 to 13.4) mumol/100 g min after occlusion periods of 30, 60 and 120 s, respectively. Concomitant with the K+ reuptake a progressive rise in LV dP/dt occurred. Adrenoceptor stimulation could not explain these findings since catecholamine release declined during occlusion and reperfusion. We suggest that increased intracellular Na+ concentration in early reperfusion stimulates the Na,K-pump and favours Ca++ entry through Na+/Ca++ exchange, thereby mediating K+ reuptake and the rise in contractility.
authors: University of Oslo, Institute for Experimental Medical Research, Ullevål Hospital, Norway.
authors: G
authors: G
authors: Aksnes
authors: O
authors: O
authors: Ellingsen
authors: D L
authors: DL
authors: Rutlen
authors: A
authors: A
authors: Ilebekk
mesh_terms: D000818:Animals; D003327:Coronary Disease / Q000378:metabolism* / Q000503:physiopathology; D005260:Female; D008297:Male; D009200:Myocardial Contraction; D009638:Norepinephrine / Q000378:metabolism; D010101:Oxygen Consumption; D011188:Potassium / Q000378:metabolism / Q000502:physiology*; D013552:Swine
chemical_list: D011188:Potassium; D009638:Norepinephrine