Calcium mobilization by cadmium or decreasing extracellular Na+ or pH in coronary endothelial cells.
Replacing extracellular Na+ with choline transiently increased cytoplasmic free Ca2+ ([Ca2+]i) more than 5-fold in coronary endothelial cells. Removing external Na+ stimulated 45Ca2+ efflux approximately 4-fold and influx approximately 1.7-fold. The stimulation of efflux was independent of extracellular Ca2+ and the osmotic Na+ substitute. The release of stored Ca2+, rather than Ca2+ influx via Na(+)-Ca2+ exchange, probably causes the increase in [Ca2+]i and 45Ca2+ efflux. Cadmium or decreasing external, not intracellular, pH transiently increased [Ca2+]i. Cd2+ and some other divalent metals also stimulated 45Ca2+ efflux. The potency order of the metals that stimulated efflux was Cd2+ greater than CO2+ greater than Ni2+ greater than Fe2+ greater than Mn2+. Incubating the cells with Zn2+ prior to assaying efflux in the absence of Zn2+ strongly inhibited the stimulation of 45Ca2+ efflux by Cd2+, pH 6, and the removal of external Na+ without affecting the stimulation of efflux by ATP. These findings support the hypothesis that certain trace metals or decreasing external Na+ or pH trigger the release of stored Ca2+ by stimulating a cell surface "receptor."
Dwyer
S D
SD
Department of Pharmacology, School of Medicine, University of Alabama, Birmingham 35294.
Zhuang
Y
Y
Smith
J B
JB
D000255:Adenosine Triphosphate / Q000502:physiology; D000818:Animals; D002104:Cadmium / Q000494:pharmacology* / Q000633:toxicity; D002118:Calcium / Q000378:metabolism*; D003331:Coronary Vessels / Q000378:metabolism; D004285:Dogs; D004730:Endothelium, Vascular / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D011188:Potassium / Q000502:physiology; D012964:Sodium / Q000502:physiology; D015032:Zinc / Q000494:pharmacology
D002104:Cadmium; D000255:Adenosine Triphosphate; D012964:Sodium; D015032:Zinc; D011188:Potassium; D002118:Calcium