Howlett. Changes in excitation-contraction coupling in an isolated ventricular myocyte model of cardiac stunning. Am J

investigate cardiac stunning, we recorded intracellular [Ca2], contractions, and electrical activity in isolated guinea pig ventricular myocytes exposed to simulated ischemia and reperfusion. After equilibration, ischemia was simulated by exposing myocytes to hypoxia, acidosis, hyperkalemia, hyper-capnia, lactate accumulation, and substrate deprivation for 30 min at 37°C. Reperfusion was simulated by exposure to Tyrode solution. Field-stimulated myocytes exhibited stun-ning upon reperfusion. By 10 min of reperfusion, contraction amplitude decreased to 43.0 5.5 % of preischemic values (n 15, P 0.05), although action potential configuration and sarcoplasmic reticulum Ca2 stores, assessed with caf-feine, were normal. Diastolic [Ca2] and Ca2 transients (fura 2) were also normal in stunned myocytes. In voltage-clamped cells, peak L-type Ca2 current was reduced t