Mobilization of free Ca2+ measured during contraction-relaxation cycles in smooth muscle cells of the porcine coronary artery using quin2.
Ca2+ mobilization in dispersed smooth muscle cells of the porcine coronary artery was investigated using the fluorescent Ca2+ indicator, quin2. The resting [Ca2+]i was 113 +/- 8 nM (a mean +/- SE), and was independent of intracellular quin2 concentrations. Acetylcholine (ACh; over 10 nM) or caffeine (over 3 mM) transiently increased the intensity of fluorescence, thereby reflecting the elevation of intracellular free Ca2+ (Ca2+ transient), while excess K+ gradually increased and maintained the intensity of fluorescence. Application of EGTA reduced the resting intensity of the fluorescence and blocked the K+-induced Ca2+ transient, but did not suppress the ACh- or caffeine-induced ones. Nisoldipine (0.1 microM) did not affect the resting intensity of the fluorescence. This agent blocked the K+ induced but not the ACh- or caffeine- induced Ca2+ transient. Thus, sources of Ca2+ contributing to the K+ -induced Ca2+ transient differ from those evoked by other agents. The amount of Ca2+, as estimated from the increased Ca2+ transient by caffeine or ACh, was increased in proportion to the excess K+-induced influx of Ca2+.
Sumimoto
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Kuriyama
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D000109:Acetylcholine / Q000494:pharmacology; D000634:Aminoquinolines; D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D002121:Calcium Channel Blockers / Q000494:pharmacology; D003331:Coronary Vessels / Q000502:physiology*; D004533:Egtazic Acid / Q000494:pharmacology; D005456:Fluorescent Dyes; D066298:In Vitro Techniques; D007700:Kinetics; D009119:Muscle Contraction / Q000187:drug effects; D009126:Muscle Relaxation / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000502:physiology*; D009543:Nifedipine / Q000031:analogs & derivatives / Q000494:pharmacology; D015737:Nisoldipine; D011188:Potassium / Q000494:pharmacology; D013552:Swine
D000634:Aminoquinolines; D002121:Calcium Channel Blockers; D005456:Fluorescent Dyes; D002110:Caffeine; D015737:Nisoldipine; D004533:Egtazic Acid; D009543:Nifedipine; D000109:Acetylcholine; C035739:Quin2; D011188:Potassium; D002118:Calcium