Calcium Mobilization and Exocytosis After One Mechanical Stretch of Lung Epithelial Cells

TLDR

Deep lung inflation stimulates surfactant secretion, but the underlying mechanisms remain unknown. The study tested whether mechanical distension directly stimulates type II cells to secrete surfactant by stretching cultured cells on silastic membranes. Intracellular Ca²⁺ levels were measured in single cells before and after stretching. A single stretch induced a brief (<60 s) rise in cytosolic Ca²⁺ followed by a sustained (15–30 min) increase in surfactant secretion, with both Ca mobilization and exocytosis dose‑dependent on stretch magnitude, indicating that mechanical forces can trigger complex cellular events in non‑neural, non‑muscle cells and may regulate normal lung function.

Abstract

Deep inflation of the lung stimulates surfactant secretion by unknown mechanisms. The hypothesis that mechanical distension directly stimulates type II cells to secrete surfactant was tested by stretching type II cells cultured on silastic membranes. The intracellular Ca 2+ concentration was measured in single cells, before and after stretching. A single stretch of alveolar type II cells caused a transient (less than 60 seconds) increase in cytosolic Ca 2+ followed by a sustained (15 to 30 minutes) stimulation of surfactant secretion. Both Ca 2+ mobilization and exocytosis exhibited dose-dependence to the magnitude of the stretch-stimulus. Thus, mechanical factors can trigger complex cellular events in nonneuron, nonmuscle cells and may be involved in regulating normal lung functions.