Protein synthesis by human fetal lung

Abstract

Biochemical and morphologic studies have shown that proteins and carbohydrate-protein complexes, in addition to phospholipids, are present in the alveolar surface layer. For this reason the study of lung protein synthesis in parallel with phospholipid biosynthesis and its regulation is of interest. The data obtained show that from 16 to 24 weeks' of gestation the human fetal lung rapidly incorporated 14C-leucine into proteins from the particulate fraction and 105,000 × g tissue supernatant fraction. The distribution of radioactivity between protein fractions after gel filtration on Sephadex G-200 revealed three major peaks of radioactivity. According to our results the protein, detected at the site of the 7S peak of normal serum, was synthesized in vitro by human lung tissue, as was a more rapidly labeled 19S protein which was released into the incubation medium. The addition of prolactin and cortisone to the incubation medium led to a dose-dependent inhibition of total protein synthesis by the human fetal lung in vitro. The significant decrease in 14C-leucine incorporation was noticed in proteins eluted from the Sephadex G-200 column in fractions corresponding to the 19S and 7S peaks of normal human sera.