Calcium current in congestive heart failure of hamster cardiomyopathy.

L-type calcium current (ICa) was examined using the whole cell patch-clamp method in ventricular cardiomyocytes of 400- to 458-day-old cardiomyopathic (CM) Syrian hamsters (BIO 14.6 strain) that exhibited pathology consistent with congestive heart failure. Controls were comparably aged normal (N) hamsters (BIO F1B strain). At -35-mV holding potential, ICa, normalized to picofarads of membrane capacitance, was significantly lower in amplitude in cells of CM vs. N at 300-ms duration voltage command steps of -25 to +25 mV (10-mV increments from -25 to +65 mV). Estimates of reversal potential for ICa were similar between strains, whereas average maximum specific conductance was significantly greater for N than for CM. Inactivation time constants (biexponential) and the time constant for recovery from inactivation were significantly longer for CM vs. N. Steady-state activation and inactivation data were similar between strains by Boltzmann fit. Results suggest that ICa amplitude is below normal in CM, possibly due to decreased conductance or density of functional L-type channels. This may contribute to the depressed contractions in this model of congestive heart failure.