Front-surface fluorometry with fura-2 and effects of nitroglycerin on cytosolic calcium concentrations and on tension in the coronary artery of the pig.
1. By use of front-surface fluorometry and fura-2-loaded strips of the coronary artery of the pig, the effects of nitroglycerin (NG) on cytosolic Ca2+ concentrations ([Ca2+]i) and on tension development were measured simultaneously. 2. Both high K+ depolarization and histamine increased [Ca2+]i and tension in a concentration-dependent manner. However, the tension development in relation to the [Ca2+]i increase ([Ca2+]i-tension relation) observed with histamine was much greater than that observed with K+ depolarization. 3. NG reduced in a concentration-dependent manner both [Ca2+]i and tension, irrespective of whether the vascular strips were in a resting state or during exposure to high K+ or to histamine stimulation. However, the extent of reduction in tension (relaxation) was greater than that expected from the reduction in [Ca2+]i based on the [Ca2+]i-tension relationship observed with K(+)-depolarization. 4. In the absence of extracellular Ca2+, NG depleted stored Ca2+ and also inhibited Ca2+ release from histamine-sensitive stores, but had no effect on the caffeine-sensitive stores. NG inhibited the caffeine-induced tension development with no change in [Ca2+]i. 5. We suggest that NG relaxes the coronary artery of the pig by reducing [Ca2+]i and also by directly controlling contractile elements through second messengers not related to changes in [Ca2+]i.
Abe
S
S
Division of Molecular Cardiology, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Kanaide
H
H
Nakamura
M
M
D000818:Animals; D002110:Caffeine / Q000494:pharmacology; D002118:Calcium / Q000378:metabolism*; D003331:Coronary Vessels / Q000187:drug effects / Q000502:physiology; D003600:Cytosol / Q000378:metabolism; D016257:Fura-2; D006632:Histamine / Q000494:pharmacology; D066298:In Vitro Techniques; D008564:Membrane Potentials / Q000187:drug effects; D009131:Muscle, Smooth, Vascular / Q000187:drug effects* / Q000502:physiology; D005996:Nitroglycerin / Q000494:pharmacology*; D011188:Potassium / Q000494:pharmacology; D013050:Spectrometry, Fluorescence; D013552:Swine; D014664:Vasodilation / Q000187:drug effects
D002110:Caffeine; D006632:Histamine; D005996:Nitroglycerin; D011188:Potassium; D002118:Calcium; D016257:Fura-2