COLLAGEN AND ELASTIN IN RABBIT FETAL LUNG - ONTOGENY AND EFFECTS OF STEROIDS

Ontogeny of lung collagen and elastin were studied in fetal rabbit fro m day 25 to term. Collagen (isolated by hot trichloroacetic acid treat ment) and elastin (contained in the residue) were hydrolyzed and the h ydroxyproline and desmosine quantitated by hplc. Hydroxyproline slight ly increased from day 25 to day 30 (204 to 244 mug/100g dry weight). O ver the same period desmosine increased from 2.2 to 5.1 mug/100 mg dry weight (P<0.01). The effect of antenatal corticosteroids on the lung of prematurely-delivered fetuses was also evaluated. Betamethasone (B) was given to pregnant does at a dose of 0.2 mg/kg 24 and 48 h before delivery of the fetuses at 26, 27 and 28 days. In treated animals elas tin concentration increased significantly by about 22% on day 26 (P=0. 05), by 29% on day (P<0.02) and by 47% on day 28 (P<0.02). Hydroxyprol ine was not affected by steroid treatment at any gestational age. This suggests that steroids affect fetal lung development also via changes in connective tissue.