A calcium conducting channel akin to a calcium pump |
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Authors: | Jinsong Wang John M Tang Robert S Eisenberg |
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Institution: | (1) Department of Physiology, Rush Medical College, 60612 Chicago, Illinois |
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Abstract: | Summary Calcium conducting channels were studied in blebs of sarcoplasmic reticulum described by Stein & Palade (1988). The calcium channels had at least three conductance states (70 pS, 50 pS and 37 pS) and were weakly selective for calcium ions, with a permeability ratio Ca2+ to K+ of about 3.4. The open probability of the channel was strongly voltage dependent, decreasing at positive membrane voltages. 10 m ryanodine and 5 m ruthenium red had no effect on this channel; neither did millimolar concentrations of ATP, Mg2+, caffeine, and Ca2+, implying that the calcium conducting channels are not ryanodine receptors. Several calcium pump inhibitors—namely, vanadate, AlF
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, reactive red 120, and cyclopiazonic acid—had obvious effects on the calcium conducting channels, suggesting that the calcium conducting channel of SR membrane blebs is some form of the SR calcium pump.We thank the National Science Foundation for steadfast support.We thank Drs. F. Cohen, A. Fox, R. Levis and E. Rios for much useful help and criticism and Dr. G. Inesi for sending us his paper while in press. |
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Keywords: | calcium pump sarcoplasmic reticulum calcium channel ryanodine receptor |
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