Effect of epidermal growth factor on enzymes of phospholipid biosynthesis in lung and liver of fetal rat in vivo and in vitro

Epidermal growth factor (EGF), a mitogenic polypeptide that binds to cell s urface receptors, is an important regulator of cell differentiation and fet al lung surfactant synthesis, and may be used as a potential novel therapeu tic agent in prematurity. Nevertheless, the distinct role in lung developme nt and its mechanisms of action are not well understood. We investigated in vivo the systemic effect of intrafetally administered EGF (200 ng/g fetal body weight) and maternally administered dexamethasone (DEXA; 0.2 and 2.0 m g/kg maternal body weight) on the activity of important enzymes of the phos pholipid synthesis in the fetal rat lung and liver: choline kinase (EC 2.7. 1.32), cholinephosphate cytidyltransferase (EC 2.7.7.15), choline phosphotr ansferase (EC 2.7.8.2), lysolecithin acyltransferase (EC 2.3.1.23) and glyc erolphosphate phosphatidyltransferase (EC 2.7.8.5). Additionally, in vivo a nd in vitro effects of DEXA on EGF receptor synthesis, and the effects of E GF on protein content and morphogenesis of the fetal rat lung organoid cult ure, were evaluated. Whereas DEXA induced the activity of all investigated enzymes of phospholipid synthesis and increased EGF receptor synthesis, EGF has no effects on the enzymes, either in vivo or in vitro. EGF enhanced pr otein synthesis and morphogenesis in vitro. With respect to our data and th e literature, we hypothesize that DEXA and EGF may act on different cellula r sides. Whereas glucocorticoids induce surfactant phospholipid synthesis, EGF should be more involved in cell proliferation and morphogenesis.