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Ahstract. A fraction of isolated and enriched rodent, gastrin-containing G cells was prepared using a previously described technique (1) and employed to investigate the role of calcium in gastrin release in vitvo. Incubation of the enriched G cells in medium containing low extracellular calcium resulted in a significant, 20-40% increase in basal gastrin release. It was determined that hormone secretion is enhanced when the cells are incubated under basal conditions in medium containing low levels of calcium (0-0.3 mM CaCl,) and inhibited when the extracellular calcium concentration is increased above 2.4 mM. Addition of Verapamil, a drug which prevents calcium entry into isolated cells and accelerates calcium efflux, to the medium at a final concentration of 10 pM, induced a significant 2-2.5 fold increase in gastrin release. Peptone-stimulated gastrin release was not influenced by either Verapamil or incubation of the cells in calcium-free medium. The results suggest that inhibition of calcium influx or acceleration of calcium efflux from the G cell may be a critical step in the initiation of gastrin release.

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