Ellingsen O, Aksnes G, Ilebekk A
Institute for Experimental Medical Research, University of Oslo, Norway.
Acta Physiol Scand. 1992 Jun;145(2):99-104. doi: 10.1111/j.1748-1716.1992.tb09344.x.
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.
为了确定在体内增加细胞外和细胞内钙浓度是否能模拟儿茶酚胺诱导的心肌钾摄取，我们用PVC-缬氨霉素电极测量了9只麻醉开胸猪动脉和冠状窦血中心肌钾平衡的变化。向左冠状动脉内输注氯化钙（200 - 400 μmol·min⁻¹）使冠状窦血钙浓度从2.29（2.19 - 2.42）mmol·L⁻¹增加到4.63（3.76 - 5.67）mmol·L⁻¹（中位数，95%置信区间，P = 0.01），表明心肌细胞外钙浓度有类似增加。收缩性指标左心室dp/dt增加了95（76 - 147）%，表明细胞内钙浓度有显著增加。在氯化钙输注期间，冠状窦钾浓度下降至比基线低0.12（0.09 - 0.17）mmol·L⁻¹的最低点（P = 0.008），而动脉浓度保持不变。心肌钾摄取峰值为18（7 - 32）μmol·min⁻¹·100 g⁻¹，在输注开始后150（110 - 195）秒出现。在使用哌唑嗪和普萘洛尔阻断肾上腺素能受体后，该反应保持不变。长时间输注氯化钙导致心肌净钾丢失，并伴有心肌缺血的代谢和血流动力学指标。这些发现与完整跳动的猪心脏中钠钾泵活性增强以响应细胞外和细胞内钙浓度增加是一致的。
