Characterization of voltage-dependent calcium channels expressed in Xenopus oocytes injected with mRNA from rat heart.

摘要: 1. The properties of voltage dependent cardiac Ca channels expressed in Xenopus laevis oocytes after injection mRNA from rat heart were investigated using the double-microelectrode voltage-clamp technique. 2. Endogenous Ba current (IBa,E) and (IBa,C) studied at various external concentrations barium (Ba2+). These two entities could be distinguished by their amplitude pharmacology. IBa,C was more sensitive to inorganic channel blocker manganese (Mn2+). contaminant IBa,E presented dependence identical IBa,C, but negligible presence a low Ba2+ concentration (2 mM). 3. In 2 mM-Ba2+, activated -35 mV, peaked -14 reversed +26 mV. Steady-state inactivation properties, consideration half-inactivation potential also typical L-type currents. However, decay very slow (time constant near 600 ms). No evidence for expression transient (T-type) found. 4. enhanced exposure 1,4-dihydropyridine (DHP) agonist Bay K 8644. enhancement (maximum -30 +/- 5 mV) associated with slowing decay. Current-voltage concentration-response curves obtained revealed an antagonism between 1,4-DHP Similar results found (-)Bay 8644 pure isomer. 5. We conclude that injected only high threshold, long-lasting or channels. availability quantitative pharmacological studies has been demonstrated.