Calcium currents in the A7r5 smooth muscle-derived cell line. Increase in current and selective removal of voltage-dependent inactivation by intracellular trypsin.
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.
Obejero-Paz
C A
CA
Department of Physiology and Biophysics, Case Western Reserve University, Cleveland, Ohio 44106.
Jones
S W
SW
Scarpa
A
A
D000818:Animals; D001464:Barium / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects / Q000502:physiology; D002118:Calcium / Q000493:pharmacokinetics* / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000502:physiology; D002460:Cell Line; D004305:Dose-Response Relationship, Drug; D004553:Electric Conductivity / Q000187:drug effects / Q000502:physiology; D004558:Electric Stimulation; D009131:Muscle, Smooth, Vascular / Q000166:cytology* / Q000502:physiology; D014357:Trypsin / Q000494:pharmacology*
D015220:Calcium Channels; D001464:Barium; D014357:Trypsin; D002118:Calcium