Nitric oxide induces intracellular Ca2+ mobilization and increases secretion of incorporated 5‐hydroxytryptamine in rat pancreatic β‐cells

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Abstract
This study is the first to demonstrate that low concentrations of aqueous NO induce intracellular Ca2+ mobilization and an increase in secretory activity of rat pancreatic β‐cells. Application of NO solution (2 μM) resulted in a transient increase in the free intracellular Ca2+ concentration ([Ca2+]i) of isolated cells, as assessed by video ratio imaging and single wavelength microfluorimetry. Amperometry revealed a simultaneous increase in the release of preloaded 5‐hydroxytryptamine from the isolated cells. The NO‐induced Ca2+ response primarily involves mobilization of endoplasmic reticulum Ca2+ stores, since the response was retained when cells were transferred to low Ca2+ medium, and completely inhibited when cells were pretreated with 10 μM thapsigargin. The Ca2+ response was also inhibited when cells were incubated with a high concentration of ryanodine (200 μM), suggesting that Ca2+ mobilization is via a ryanodine‐sensitive store.