Calcium currents in the A7r5 smooth muscle-derived cell line. Increase in current and selective removal of voltage-dependent inactivation by intracellular trypsin |
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Authors: | C A Obejero-Paz S W Jones A Scarpa |
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Institution: | Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106. |
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Abstract: | We studied the effects of trypsin on L-type calcium current in the A7r5 smooth muscle cell line. Intracellular dialysis with trypsin increased the whole-cell current up to fivefold. The effect was concentration dependent, and was prevented by soybean trypsin inhibitor. Ensemble analysis indicated an increase in the number of functional channels, and possibly a smaller increase in the open probability, with no change in the single channel current. The shape of the current-voltage curve was unaffected. Trypsin also nearly eliminated inactivation of currents carried by Ba2+, but had little or no effect on the rapid inactivation process in Ca2+, This indicates that trypsin removes voltage-dependent but not Ca(2+)-dependent inactivation, suggesting the existence of distinct protein domains for these two mechanisms of calcium channel inactivation. |
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