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KMID : 0811719980020030313
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Korean Journal of Physiology & Pharmacology
1998 Volume.2 No. 3 p.313 ~ p.322
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Characteristics of Ca2＋ Stores in Rabbit Cerebral Artery Myocytes
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Sung Joon Kim
Jin Kyung Kim/Insuk So/Suk Hyo Suh/Sang Jin Lee/Ki Whan Kim
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Abstract
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In a myocyte freshly isolated from rabbit cerebral artery, the characteristics of Ca2+ release by histamine or caffeine were studied by microspectrofluorimetry using a Ca2+?binding fluorescent dye, fura-2. Histamine (5 μM) or caffeine (10 mM) induced a phasic rise of cytoplasmic free Ca2+ concentration ([Ca2+]C) which could occur repetitively with extracellular Ca2+ but only once or twice in Ca2+?free bathing solution. Also, the treatment with inhibitor of sarcoplasmic reticulum Ca2+?ATPase suppressed the rise of [Ca2+]C by histamine or caffeine. In Ca2+?free bathing solution, short application of caffeine in advance markedly attenuated the effect of histamine, and vice versa. In normal Ca2+?containing solution with ryanodine (2 μM), the caffeine-induced rise of [Ca2+]C occurred only once and in this condition, the response to histamine was also suppressed. On the other hand, in the presence of ryanodine, histamine could induce repetitive rise of [Ca2+]C while the amplitude of peak rise became stepwisely decreased and eventually disappeared. These results suggest that two different Ca2+?release mechanisms (caffeine-sensitive and histamine-sensitive) are present in rabbit cerebral artery myocyte and the corresponding pools overlap each other functionally. Increase of [Ca2+]C by histamine seems to partially activate ryanodine receptors present in caffeine-sensitive pool.
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KEYWORD
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Smooth muscle, Ca2＋ concentration, Ca2＋ pool, Histamine, Caffeine,
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