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Science 30 May 1986:
Vol. 232. no. 4754, pp. 1143 - 1145
DOI: 10.1126/science.3704641
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Articles

Science, Vol 232, Issue 4754, 1143-1145
Copyright © 1986 by American Association for the Advancement of Science

articles

Cytosolic calcium during contraction of isolated mammalian gastric muscle cells

KN Bitar, P Bradford, JW Putney Jr, and GM Makhlouf

During activation of visceral smooth muscle there is an increase in cytosolic-free calcium, but the source (intracellular calcium release or calcium influx), kinetics, and stoichiometry of this increase have not been determined. Here, the fluorescent indicator, quin2-acetoxymethyl ester, was used to measure directly cytosolic-free calcium during contraction of isolated stomach muscle cells induced by the two neuropeptides cholecystokinin-octapeptide and Met-enkephalin as well as acetylcholine. An increase in cytosolic-free calcium was seen that was (i) dependent on the concentration of contractile agonist, (ii) derived from intracellular sources (that is, not significantly affected by removal of ambient calcium or addition of a calcium channel blocker), and (iii) kinetically and stoichiometrically related to net calcium efflux and contraction. In contrast, the increase in cytosolic-free calcium induced by depolarizing concentrations of potassium was caused by influx of calcium through voltage-dependent calcium channels.


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