1. Changes in cytoplasmic Ca2+ concentration ([Ca2+](i)) were measured simultaneously with force by a microfluorometric method using a calcium indicator, fura-2, in canine coronary arterial smooth muscle cells. 2. Depolarization by high (30-90 mM) KCl-physiological salt solution (PSS) produced concentration-dependent increases in force and [Ca2+](i). 3. The KCl-induced increase in [Ca2+](i) was abolished by Ca2+-free conditions and almost abolished by verapamil 10-5 M, suggesting that it was entirely due to the increased Ca2+ influx through voltage-dependent Ca2+ channels. 4. The [Ca2+](i)-force relationship in the presence of verapamil was not distinguishable from that of control. 5. Nitroglycerin produced a concentration-dependent, reversible contraction of the coronary artery that had been contracted by high KCl-PSS, without reduction of the increased [Ca2+](i). 6. The KCl-induced increase in [Ca2+](i) was not affected by nitroglycerin and in the presence of nitroglycerin it was abolished by 10-5 M verapamil suggesting that it was caused by the influx of extracellular Ca2+. 7. The [Ca2+](i)-force curve was shifted to the right by nitroglycerin. 8. It is likely that nitroglycerin relaxes the coronary arterial smooth muscle by reducing the amount of myosin light chain phosphorylation even in the presence of raised [Ca2+](i) produced by increased Ca2+ influx following depolarization.
|Number of pages||14|
|Journal||British Journal of Pharmacology|
|Publication status||Published - 1989|
ASJC Scopus subject areas