Surfactant Phospholipid Metabolism in 3-Day and 3-Day Postmature Rabbits In Vivo

Abstract

Summary remain controversial (3 1). Radiolabeled phospholipid precursorsThree-day-old normal and M a y postmature rabbits (prepared by human chorionic gonadotropin treatment of the does) were given injections of the radiolabeled phospholipid precursors pnlmitic acid, choline, and glycerol. The specific activities as c p d pool phospholipid phosphate were measured for phosphatidykholine, disaturated phosphatidylcholine, phosphatidylglycerol, phosphatidylinositol, and phosphatidylethanolPmine from lung and alveolar wash fraction lipid extracts of May-old rabbits. Specific activities similarlv were measured for ~hos~hatidvlcholine and disaturated ph~s~hatid~lcholine from p&tmabre ribbits. Curves describing the appearance of labeled phospholipids into the alv* lar wash fractiondemonstrated that 6 both 3-day and postmature rabbits, phospholipid secretion was delayed for 3 to 4 hr. Thereafter, there was a rapid accumulation of labeled phospholipids until 12 to 16 hr after labeled precursor injection. The curves were similar for all measured phospholipids and all labeled precursors studied. The phospholipid compositions of lung and alveolar wash fraction lipid extracts were determined by analysis of the various phospholipids separated by two-dimensional thin-layer chromatography. Forty percent of lung samples and 35% of alveolar wash samples from postmature rabbits contained no detectable phosphatidylglycerol, whereas all 22 lung and surfactant samples from 3-day-old rabbits contained this phospholipid. Speculation