Rat lung surfactant kinetics biochemical and morphometric correlation

Abstract

Biochemical and morphometric techniques were combined to estimate the distribution and flux of rat lung disaturated phosphatidylcholine (DSPC) in surfactant pathways. There were 126 .+-. 8 .times. 106 alveolar epithelial type II (AEP II) cells/lung, each containing 150 .+-. 30 lamellar bodies (LB). High yields of LB were isolated by centrifugation of lung homogenates with a discontinuous sucrose density gradient. Measurement of DSPC in LB and alveolar lavage (LV) material demonstrated that only 30% (LB 14%, LV 16%) of lung DSPC was present in these surfactant compartments. Radiolabeling of lung DSPC with [14C]palmitate demonstrated a product-precursor relationship between LB and LV and a surfactant-associated DSPC flux of 90 .mu.g .cntdot. lung-1 .cntdot. h-1. Although only 16% of lung DSPC is in an intracellular surfactant pathway at any time, all this DSPC is ultimately secreted onto the alveolar surface.