Phospholipase activities of surfactant fractions and their role in the morphological change in surfactants in vitro.

: Rat lung surfactants including lamellar body, common myelin and tubular myelin were evaluated for enzyme activities of phospholipase A and phospholipase C using [14C] phosphatidylcholine as the substrate. The metabolic profiles of phosphatidylcholine were correlated with ultrastructural changes of each fraction in vitro incubation to elucidate whether any of these enzymes has a role in the morphological change. Lamellar body showed phospholipase A and phospholipase C activities at neutral pH. Electron microscopic observation showed that although these enzymes had no direct role in change of integration of the lamellar body to lattice tubule, phospholipase C had a role in modulation of the lamellar body to loose lamellae, and phospholipase A had a role in degradation of lattice integration.