Sodium-dependent calcium efflux from adrenal chromaffin cells following exocytosis: Possible role of secretory vesicle membranes

Chung Ren Jan, Allan S. Schneider*

*Corresponding author for this work

Research output: Contribution to journalJournal Article peer-review

15 Scopus citations

Abstract

Although cytosolic Ca2+ transients are known to influence the magnitude and duration of hormone and neurotransmitter release, the processes regulating the decay of such transients after cell stimulation are not well understood. Na+-dependent Ca2+ efflux across the secretory vesicle membrane, following its incorporation into the plasma membrane, may play a significant role in Ca2+ efflux after stimulation of secretion. We have measured an enhanced 45Ca2+ efflux from cultured bovine adrenal chromaffin cells following cell stimulation with depolarizing medium (75 mM K+) or nicotine (10 μM). Such stimulation also causes Ca2+ uptake via voltage-gated Ca2+ channels and secretion of catecholamines. Na+ replacement with any of several substitutes (N-methyl-glucamine, Li+, choline, or sucrose) during cell stimulation inhibited the enhanced 45Ca2+ efflux, indicating an Na+-dependent Ca2+ efflux process. Na+ deprivation did not inhibit 45Ca2+ uptake or catecholamine secretion evoked by elevated K+. Suppression of exocytotic incorporation of secretory vesicle membranes into the plasma membrane with hypertonic medium (620 mOsm) or by lowering temperature to 12 °C inhibited K+-stimulated 45Ca2+ efflux in Na+-containing medium but did not inhibit the stimulated 45Ca2+ uptake. Enhancement of exocytotic secretion with pertussis toxin resulted in an enhanced 45Ca2+ efflux without affecting calcium uptake. The combined results suggest that Na+-dependent Ca2+ efflux across secretory vesicle membranes, following their incorporation into the plasma membrane during exocytosis, plays a significant role in regulating calcium efflux and the decay of cytosolic Ca2+ in adrenal chromaffin cells and possibly in related secretory cells.

Original languageEnglish
Pages (from-to)9695-9700
Number of pages6
JournalJournal of Biological Chemistry
Volume267
Issue number14
StatePublished - 15 05 1992
Externally publishedYes

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