Developmental changes in calcium currents of rabbit ventricular cells.

We investigated the postnatal development of L-type Ca2+ current (ICa) in enzymatically isolated adult (AD) and newborn (NB) (1-3-day-old) rabbit ventricular cells using the whole-cell, patch-clamp method. ICa was recorded with Cs(+)-rich pipettes and a Na(+)- and K(+)-free bath solution at 36 degrees C to eliminate other currents. ICa density (obtained by normalizing ICa to the cell capacitance) was significantly higher in AD cells than in NB cells at potential levels between 0 and +50 mV with 1.8 mM Ca2+ as the charge carrier. There was no shift in the current-voltage relation between AD and NB cells. The maximum ICa density was 9.9 +/- 2.0 pA/pF at 14 +/- 5 mV in AD cells (n = 11) compared with 5.6 +/- 2.0 pA/pF at 13 +/- 5 mV in NB cells (n = 7) (mean +/- SD). Time to half inactivation (T 1/2) showed a nearly U-shaped relation to membrane potentials from -10 to +30 mV with the shortest T 1/2 at the potential giving the maximum ICa density in both groups. T 1/2 at 0 and +10 mV was slightly but significantly longer in NB cells (16.8 +/- 4.6 and 13.5 +/- 2.4 msec, respectively) than in AD cells (12.6 +/- 3.0 and 10.6 +/0 1.5 msec).(ABSTRACT TRUNCATED AT 250 WORDS)