Developmental changes in phosphatidylinositol transfer protein concentration and phospholipid transfer activities in rat type II cells

The phospholipid transfer proteins (PLTPs) are cytosolic proteins that have been characterized by their ability to facilitate the transfer of phosphol ipids between membranes in vitro. The goals of this study mere to determine whether PITP alpha concentration and phospholipid transfer activities are enriched in type II calls compared with whole lung and to determine the dev elopmental changes in PITP alpha concentration and phospholipid transfer ac tivities during kits gestation and newborn period. The concentration of PIT P alpha in type II cell cytosol measured by enyme-linked immunosorbent assa y (ELISA) increased during late fetal gestation to 2.2-fold adult levels an d declined 41% during the first postnatal day. However, compared to whole a dult lung cytosol, type II cell cytosol was not significantly enriched with PITP alpha. Phospholipid transfer activities were determined by a vesicle- rat lung membrane transfer assay. In adult lung, transfer activities for al l the phospholipids were enriched in adult type 17 cell cytosol compared to whole lung cytosol (phosphatidylglycerol [PG], 12.5-fold; phosphatidylinos itol [PI], 9.2-fold; phosphatidylcholine [PC], 6.5-fold; and phosphatidylet anolamine [PE], 6.6-fold; P < .05 in each case). The rate of phospholipid t ransfer in type LT cell cytosol increased during late fetal gestation to le vels 4.9 (PG), 3.7 (PI), and 2.8 (PC) times greater than adult levels. In c ytosol from cells from different stages, the order of trans,fer rate was PG > PI > PC > PE. PITP alpha immunodepletion of adult type II cytosol did no t significantly affect phospholipid transfer activities, suggesting that ot her PLTPs are responsible for the majority of the observed transfer activit ies in these cells. Developmental increases in PITP alpha concentration and other PLTPs Parallel developmental changes in type II cell surfactant phos pholipid metabolism, suggesting a possible role of these transfer proteins in the unique function of the type II cell.