Beta-adrenergic mobilization of Ca2+ from an intracellular store in rat submandibular acini.

Increases in cytoplasmic free Ca2+ concentration in rat submandibular acini were observed in response to isoprenaline (10 microM), noradrenaline (10 microM) and carbamoylcholine (10 microM). Noradrenaline and carbamoylcholine responses were decreased to 27% and 33% respectively in the absence of extracellular Ca2+, suggesting a major requirement for Ca2+ entry. beta-Adrenergic stimulation elicited a small (35-40 nM) free Ca2+ rise, approx. 75% of which was mobilized from an intracellular store. Results suggest that this Ca2+ rise is a key event in the physiological triggering of mucin secretion by exocytosis.