Possible mechanisms of stimulus-induced vacuolation in serous cells of tracheal secretory glands

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Abstract
Several factors affecting the stimulus-induced vacuolation in cat tracheal submucosal glands described in a companion paper [Am. J. Physiol. 241 (Cell Physiol. 10): C18–C24, 1981] were examined. Stimulation with predominantly alpha-adrenergic, beta-adrenergic, and cholinergic agonists at various concentrations and in the presence of appropriate blockers showed that alpha-adrenergic or cholinergic stimulation is more effective in inducing vacuolation than beta-adrenergic stimulation. In addition, Ca- or HCO3- deficient incubation medium or low incubation temperature either blocked or significantly decreased the vacuolation response. Stimulation in the presence of the Na-K-ATPase inhibitor ouabain prevented vacuolation. The known roles of these factors in fluid transport are consistent with the possibility that stimulus-induced vacuolation possibly arises in response to disturbances in cytoplasmic fluid, which are induced in the secretory cell when the fluid component of secretion is intensely stimulated. A model is presented that possibly relates the observed responses to intracellular event and suggests the possibility of ion pumps in the apical membrane.