Spatial localization of the stimulus‐induced rise in cytosolic Ca2+ in bovine adrenal chromaffin cells

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Abstract
The spatial distribution of the intracellular free Ca2+ (Ca2+ i) rise elicited by different stimuli in bovine adrenal chromaffin cells was examined in single fura-2-loaded cells. In response to the potent secretagogues nicotine and high K+, Ca2+ i was initially localized exclusively to the entire subplasmalemmal area of the cell. In response to the ineffective secretagogues, methacholine and muscarine, the rise in Ca2+ i originated only in one pole of the cell and even at the peak of the response Ca2+ was still generally restricted to this same area of the cell. These results suggest that the triggering of exocytosis from these cells requires a specific spatial distribution of Ca2+ i.