Calcium content of the sarcoplasmic reticulum in isolated ventricular myocytes from patients with terminal heart failure. Journal of molecular and cellular cardiology

from patients with terminal heart failure compared to controls. Experiments were performed in human ventricular cells to investigate whether this reduced systolic [Ca2+]i-transient may be due to a decreased Ca2+-content of the sarcoplasmic reticulum (SR). Single myocytes were isolated from left ventricular myocardium of patients with terminal heart failure undergoing cardiac transplantation. These results were compared to those obtained from cells of healthy donor hearts that were not suitable for transplantation for technical reasons. [Ca2+]i-transients were recorded from isolated cells under voltage clamp perfused internally with the Ca2+-indicator fura-2. The Ca2+-content of the SR was estimated by rapid extracellular application of caffeine (10 m) to open the Ca2+-release channel of the SR and comparison of the caffeine-induced [Ca2+]i-transients in cells from patients with heart failure and from controls without heart failure. Upon steady-state depolarizations to +10 mV (maximum of the Ca2+-current), [Ca2+]i-transients in cells from patients with heart failure were significantly smaller than in myocytes from undiseased hearts (333±26