COMPARISON OF THE DISTINCT EFFECTS OF EPIDERMAL GROWTH-FACTOR AND BETAMETHASONE ON THE MORPHOGENESIS OF THE GAS-EXCHANGE REGION AND DIFFERENTIATION OF ALVEOLAR TYPE-II CELLS IN LUNGS OF FETAL RHESUS-MONKEYS

To compare the effects of epidermal growth factor (EGF) and betamethas one on the morphogenesis of the gas exchange region and the differenti ation of the alveolar type II cell during fetal lung development, feta l rhesus monkeys (78% gestation) were treated in utero with EGF (5.33 mg/kg total dose), betamethasone (2.6 mg/kg total dose) or the carrier , saline (control), every other day for 7 days. EGF-treated monkeys ha d significantly increased body and adrenal weights. Betamethasone-trea ted monkeys had significantly decreased body and adrenal weights. Exog enous EGF reduced cytoplasmic glycogen and increased the cytoplasmic o rganelle and SF-A content within alveolar type II cells. In contrast, exogenous betamethasone did not alter alveolar type II cell cytodiffer entiation. Neither EGF nor betamethasone treatment significantly alter ed the structure of the gas exchange region as shown by a lack of chan ge from controls in alveolar airspace size or in the fraction of the g as exchange region that was potential airspace. We conclude that at cl inically relevant doses, EGF greatly accelerates the maturation of alv eolar type II cells, whereas betamethasone does not. Exogenous EGF may act directly on alveolar type II cells because these cells contain EG F receptor. Neither EGF nor betamethasone had dramatic effects on the morphogenesis of the gas exchange region.