Interaction between injected Ca2+ and intracellular Ca2+ stores in Xenopus oocytes.
Upon two repetitive deep injections of Ca2+ into Xenopus oocyte (200-300 microns under the membrane), the amplitude of the transient Cl- current induced by the second injection is several-fold higher than that of the first one. This 'potentiation' persists even at 60-90 min intervals between injections. However, in oocytes permeabilized to Ca2+ by the ionophore A23187 in a Ca2(+)-free solution, the potentiation completely disappears after 30 min. It is proposed that the injected Ca2+ is largely taken up by the stores, whereas following the second injection, a higher proportion of Ca2+ reaches the membrane, since the stores are already loaded. In ionophore-treated oocytes, the stores lose the accumulated Ca2+ over several minutes and are then ready to take up Ca2+ again, hindering its arrival at the membrane.
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Department of Physiology and Pharmacology, Sackler Faculty of Medicine, Tel Aviv University, Ramat Aviv, Israel.
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D000818:Animals; D001693:Biological Transport, Active; D000001:Calcimycin / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002122:Calcium Chloride / Q000494:pharmacology; D002463:Cell Membrane Permeability; D018118:Chloride Channels; D002712:Chlorides / Q000378:metabolism; D005260:Female; D007473:Ion Channels / Q000378:metabolism; D008565:Membrane Proteins / Q000378:metabolism; D009865:Oocytes / Q000187:drug effects / Q000378:metabolism*; D014982:Xenopus laevis
D018118:Chloride Channels; D002712:Chlorides; D007473:Ion Channels; D008565:Membrane Proteins; D000001:Calcimycin; D002122:Calcium Chloride; D002118:Calcium