DEXAMETHASONE TREATMENT SUPPRESSES COLLAGEN-SYNTHESIS IN INFANTS WITHBRONCHOPULMONARY DYSPLASIA

Collagen is an essential component of connective tissue and is present in the pulmonary interstitium. Collagen deposition is known to increa se in many acquired chronic diseases, including bronchopulmonary dyspl asia (BPD). Urinary excretion of hydroxyproline has been used as a spe cific index of collagen synthesis. Many studies have demonstrated that dexamethasone therapy is associated with respiratory improvement in i nfants with BDP but the mechanism of this effect is not well understoo d. We postulated that in infants with BDP who receive dexamethasone, s uppression of collagen synthesis may cause respiratory improvement. Th erefore, we studied the effect of dexamethasone on respiratory status and urinary excretion of hydroxyproline in 14 ventilator-dependent inf ants with BDP. Infants received 0.5 mg/kg/day dexamethasone, tapered b y half every 3 days to complete a 12 day course. Eleven of the 14 infa nts were extubated at a mean +/- SD of 8.7 +/- 4.9 days after starting dexamethasone. Mean urinary hydroxyproline/creatinine ratios at 3, 6, 9, and 12 days of dexamethasone therapy were significantly lower than the mean pretreatment value, but after discontinuation rapidly rose t oward baseline values. Decreased urinary excretion of hydroxyproline i ndicates that dexamethasone suppressed collagen synthesis in these inf ants. We speculate that suppression of collagen synthesis reduced pulm onary inflammation and fibrosis, resulting in respiratory improvement. (C) 1993 Wiley-Liss, Inc.