[Surface-active properties of pulmonary surfactant and the functional activity of type II alveolocytes at various times of the day under experimental conditions].

Complex examination of lungs in 24 healthy guinea pigs in different periods of day using physicochemical, biochemical and electron-microscopic methods has revealed that the highest surface activity of the pulmonary surfactant (PS) is observed in the evening and at night, as phospholipids contain the highest amount of a surfactant of the phosphatidylcholine fraction the most active in the surface-active respect. An increase in the content of PS phospholipids in this period of the day appears to be a consequence of synthesis and secretion intensification in the second-type alveolocytes, that may be due to an increased effect of the vagus nerve.