Temperature-induced transitory and steady-state changes in the calcium current of guinea pig ventricular myocytes

ICa was recorded in guinea pig ventricular myocytes using the whole-cell voltage-clamp technique. The shape of the I-V relation was unaffected by temperature (21-37 degrees C) but there were large changes in ICa amplitude and time course. Steady-state responses indicated Q10's of 2.96 +/- 0.14 (amplitude), 2.52 +/- 0.13 (time to peak), and 2.82 +/- 0.28 (T1/2 inactivation) (mean +/- SD, n = 6). Quick changes in temperature (T1/2 less than 30 s) induced pronounced deviations from the steady-state Q10 relations (early depression, compensatory overshoot). Thus, cardiac ICa differs from other currents in having a high amplitude-Q10 and an oscillatory response to rapid temperature changes.