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Dynamic Ca 2+ signalling in rat arterial smooth muscle cells under the control of local renin‐angiotensin system
Author(s) -
Asada Yukinori,
Yamazawa Toshiko,
Hirose Kenzo,
Takasaka Tomonori,
Iino Masamitsu
Publication year - 1999
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1999.00497.x
Subject(s) - cyclopiazonic acid , medicine , vascular smooth muscle , angiotensin ii , endocrinology , losartan , phospholipase c , extracellular , intracellular , phenylephrine , chemistry , renin–angiotensin system , endoplasmic reticulum , myocyte , biophysics , calcium , biology , receptor , smooth muscle , biochemistry , blood pressure
1 We visualized the changes in intracellular Ca 2+ concentration ([Ca 2+ ] i ), using fluo‐3 as an indicator, in individual smooth muscle cells within intact rat tail artery preparations. 2 On average in about 45 % of the vascular smooth muscle cells we found spontaneous Ca 2+ waves and oscillations (≈0.13 Hz), which we refer to here as Ca 2+ ripples because the peak amplitude of [Ca 2+ ] i was about one‐seventh of that of Ca 2+ oscillations evoked by noradrenaline. 3 We also found another pattern of spontaneous Ca 2+ transients often in groups of two to three cells. They were rarely observed and are referred to as Ca 2+ flashes because their peak amplitude was nearly twice as large as that in noradrenaline‐evoked responses. 4 Sympathetic nerve activity was not considered responsible for the Ca 2+ ripples, and they were abolished by inhibitors of either the Ca 2+ pump in the sarcoplasmic reticulum (cyclopiazonic acid) or phospholipase C (U‐73122). 5 Both angiotensin antagonists ([Sar 1 ,Ile 8 ]‐angiotensin II and losartan) and an angiotensin converting enzyme inhibitor (captopril) inhibited the Ca 2+ ripples. 6 The extracellular Ca 2+ ‐dependent tension borne by unstimulated arterial rings was reduced by the angiotensin antagonist by ≈50 %. 7 These results indicate that the Ca 2+ ripples are generated via inositol 1,4,5‐trisphosphate‐induced Ca 2+ release from the intracellular Ca 2+ stores in response to locally produced angiotensin II, which contributes to the maintenance of vascular tone.