Inositol 1,4,5-trisphosphate-induced calcium release from platelet plasma membrane vesicles.
A platelet membrane preparation, enriched in plasma membrane markers, took up 45Ca2+ in exchange for intravesicular Na+ and released it after the addition of inositol 1,4,5-trisphosphate (IP3). The possibility that contaminating dense tubular membrane (DTS) vesicles contributed the Ca2+ released by IP3 was eliminated by the addition of vanadate to inhibit Ca+-ATPase-mediated DTS Ca2+ sequestration and by the finding that only plasma membrane vesicles exhibit Na+-dependent Ca2+ uptake. Ca2+ released by IP3 was dependent on low extravesicular Ca2+ concentrations. IP3-induced Ca2+ release was additive to that released by Na+ addition while GTP or polyethylene glycol (PEG) had no effect. These results strongly suggest that IP3 facilitates extracellular Ca2+ influx in addition to release from DTS membranes.
Rengasamy
A
A
Department of Pharmacology, University of Illinois, Chicago 60612.
Feinberg
H
H
D000255:Adenosine Triphosphate / Q000494:pharmacology; D001792:Blood Platelets / Q000187:drug effects / Q000378:metabolism*; D002118:Calcium / Q000097:blood*; D002132:Calcium Radioisotopes; D002462:Cell Membrane / Q000378:metabolism; D006160:Guanosine Triphosphate / Q000494:pharmacology; D006801:Humans; D015544:Inositol 1,4,5-Trisphosphate; D007295:Inositol Phosphates / Q000494:pharmacology*; D007700:Kinetics; D011092:Polyethylene Glycols / Q000494:pharmacology; D012964:Sodium / Q000097:blood; D013403:Sugar Phosphates / Q000494:pharmacology*; D014638:Vanadates / Q000494:pharmacology
D002132:Calcium Radioisotopes; D007295:Inositol Phosphates; D013403:Sugar Phosphates; D014638:Vanadates; D011092:Polyethylene Glycols; D015544:Inositol 1,4,5-Trisphosphate; D006160:Guanosine Triphosphate; D000255:Adenosine Triphosphate; D012964:Sodium; D002118:Calcium