Cell swelling-induced peptide hormone secretion

Cell swelling induces peptide exocytosis using unique signaling pathway. Hyposmotic-induced secretion in normal cells is not mediated by specific receptors, is independent from extra and intracellular Ca(2+), sodium and potassium channels activity, prostaglandins, leukotriens, does not involve cytoskeleton, cAMP generation, phospholipase A(2), G proteins, protein kinase C. It is promoted by swelling of the secretory vesicles. Resistance to endogenous inhibitors is frequent attribute of this type of secretion. Swelling-induced secretion involves also secretory vesicles not involved in conventional stimulation. Hyposmosis-induced insulin secretion is more sensitive to high cellular cholesterol than conventional one suggesting substantial difference between mechanisms. Participation of sequential exocytosis as dominating mechanism in swelling-induced exocytosis is hypothesized. Signaling and response in tumor cells often differs from native cells and varies markedly between cell lines. Pathogenetic implications: cell swelling could be involved in alcohol induced hypoglycemia in diabetic patients and release of peptides from pituitary and neurons. Swelling-induced products could be mediators of ischemic preconditioning involved also in protection of diabetic heart. Swelling-induced exocytosis is an ancient mechanism generally present in cells; in cells engaged in water and salt regulation is covered by specific response mediated by specific signaling. Disturbance of specific response leads to swelling-induced - inappropriate secretion of antidiuretic hormone - SIADH.