Modulation of slow gating process of calcium channels by isoprenaline in guinea-pig ventricular cells.

摘要: 1. The mechanism of enhancement Ca2+ current by isoprenaline was studied recording single-channel activity from cell-attached patches on isolated guinea-pig ventricular cells using patch pipettes containing 50 or 100 mM-Ba2+. 2. Isoprenaline (100 nM) increased the amplitude ensemble average currents increasing rate non-blank sweeps (availability). decay during 400 ms steps significantly slowed isoprenaline. However, open probability for elicited only slightly application 3. durations available state (TS) and unavailable (TF) were estimated number blank per run, respectively, applying repetitively at 2 Hz. 4. At large negative holding potentials distribution TS well fitted an exponential curve, whose time constant 1.6 to 3.1 nM-isoprenaline, while TF distributed approximately single exponentially with a 2.0 in control 1.3 presence drug. 5. depolarized slow voltage-dependent component appeared histogram its markedly decreased nM-isoprenaline. 6. availability-voltage relationship simulated Boltzmann equation maximal value 0.4 control. 0.7 curve shifted depolarizing direction 7 mV 7. availability cardiac channels forward decreasing backward both independent transitions.