AJP - Gastrointestinal and Liver Physiology, Vol 260, Issue 1 133-G141, Copyright © 1991 by American Physiological Society

ARTICLES

Inositol phosphate formation and [Ca2+]i in secretagogue-stimulated rabbit gastric mucous cells

U. Seidler and A. Pfeiffer
Department of Internal Medicine, Technical University, Munich, Federal Republic of Germany.

The formation of inositol phosphates and the changes in free intracellular Ca2+ ([Ca2+]i) in isolated rabbit gastric mucous cells during cholinergic stimulation were examined and the potential role of inositol phosphate turnover and [Ca2+]i in gastric mucus secretion evaluated. Rabbit chief and parietal cells were studied for comparison. The formation of [3H]inositol phosphates in mucous, chief, and parietal cells was stimulated in a time- and concentration-dependent fashion by acetylcholine (ACh). The ACh-induced initial [Ca2+]i peak was maximally (10(-4) M ACh) 199 +/- 8% of basal in mucous cells, 427 +/- 20% in chief, and 455 +/- 31% in parietal cells and was followed by a lower-level plateau in mucous and parietal cells but by a more rapid decline in chief cells. As in parietal and chief cells, the initial [Ca2+]i peak occurred in mucous cells in the absence of external Ca2+. ACh stimulated a mucous cell membrane Ca2(+)-entry mechanism in addition to release of Ca2+ from intracellular stores. The concentration-response relationships for the production of [3H]-inositol phosphates, the initial rise in [Ca2+]i, and the stimulation of glycoprotein secretion by ACh were virtually identical. Suppression of the [Ca2+]i rise by the intracellular Ca2(+)-chelator 1,2-bis(2-aminophenoxy)ethane-N,N,N',N'-tetraacetic acid (BAPTA) abolished the secretory response. As with many other secretory cells, gastric mucous cells possess cholinergic receptors that upon stimulation mediate the hydrolysis of phosphoinositides, a release of Ca2+ from intracellular stores, and a stimulation of Ca2+ influx through the plasma membrane.

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