Influence of Calcium on the Release of Gastrin from Isolated Rodent G Cells

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Abstract
A fraction of isolated and enriched rodent, gastrin-containing G cells was prepared using a previously described technique and employed to investigate the role of Ca in gastrin release in vitro. Incubation of the enriched G cells in medium containing low extracellular Ca resulted in a significant, 20-40% increase in basal gastrin release. Hormone secretion is enhanced when the cells are incubated under basal conditions in medium containing low levels of Ca (0-0.3 mM CaCl2) and inhibited when the extracellular Ca concentration is increased above 2.4 mM. Addition of verapamil, a drug which prevents Ca entry into isolated cells and accelerates Ca efflux, to the medium at a final concentration of 10 .mu.M, induced a significant 2- to 2.5-fold increase in gastrin release. Peptone-stimulated gastrin release was not influenced by either verapamil or incubation of the cells in Ca-free medium. Inhibition of Ca influx or acceleration of Ca efflux from the G cell may be a critical step in the initiation of gastrin release.