K+-depolarization induces a direct release of Ca2+ from intracellular storage sites in cultured vascular smooth muscle cells from rat aorta.
Using an intracellularly trapped dye, quin 2, effects of K+-depolarization on cytosolic free calcium concentrations were recorded microfluorometrically in rat aorta vascular smooth muscle cells in primary culture. When the cells were exposed to high extracellular K+ in Ca+-free media containing 2mM EGTA, there was a transient and dose-dependent elevation of cytosolic Ca2+ concentrations. However, the concentration of the cytosolic Ca2+ was not elevated when the intracellularly stored Ca2+ was depleted by the repetitive treatment with caffeine prior to the application of high K+. Thus depolarization of plasma membrane, per se, directly induces a release of Ca2+ from intracellular storage sites in vascular smooth muscle cells, and the main fraction of this released Ca2+ is derived from the caffeine sensitive storage sites; perhaps from the sarcoplasmic reticulum.
D000634:Aminoquinolines; D000818:Animals; D001826:Body Fluids / Q000378:metabolism*; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D004533:Egtazic Acid / Q000494:pharmacology; D005454:Fluorescence Polarization; D007424:Intracellular Fluid / Q000378:metabolism*; D009131:Muscle, Smooth, Vascular / Q000166:cytology / Q000378:metabolism*; D005996:Nitroglycerin / Q000494:pharmacology; D011188:Potassium / Q000378:metabolism*; D051381:Rats
D000634:Aminoquinolines; D002110:Caffeine; D004533:Egtazic Acid; C035738:Quin2-acetoxymethyl ester; D005996:Nitroglycerin; D011188:Potassium; D002118:Calcium