AJP - Gastrointestinal and Liver Physiology, Vol 257, Issue 2 308-G312, Copyright © 1989 by American Physiological Society

ARTICLES

Carbachol inhibits stimulant-induced increases in fundic D-cell cytosolic Ca2+ concentration

T. Chiba, T. Fujita and T. Yamada
Third Department of Internal Medicine, Kobe University School of Medicine, Japan.

We undertook these studies to examine the mechanisms by which carbachol inhibits somatostatin release. For these studies, we utilized cultured D-cells isolated from the canine gastric fundus. Carbachol inhibited somatostatin release induced by both pentagastrin and 12-O-tetradecanoyl-phorbol-13-acetate but did not alter the redistribution of protein kinase C induced by these agents. In contrast, carbachol diminished the increase in D-cell cytosolic free calcium levels ([Ca2+]i) induced by pentagastrin, and this effect was no longer evident after pretreatment of D-cells with pertussis toxin. Although carbachol by itself had no effect on [Ca2+]i, after pretreatment of D-cells with pertussis toxin, carbachol both enhanced [Ca2+]i and stimulated somatostatin release. These data indicate that carbachol activates signals in D-cells that result in both increase and decrease in [Ca2+]i. The latter effect, which appears to be mediated via a pertussis toxin-sensitive guanine nucleotide binding protein, may be one mechanism responsible for cholinergic inhibition of somatostatin release.

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