Response of cardiac myocytes to increasing concentrations of the β-adrenergic agonist, ISO, alone and with incubation with NAC (10−3 M) on change in Ca2+ concentration (A), Ca2+ departure velocity (B), and Ca2+ return velocity (C). Values are means ± SE; n = 15. Con vs. Stress, *P < 0.01; Stress vs. Stress + NAC, #P < 0.01.