COMBINED EFFECTS OF FETAL BETA-AGONIST STIMULATION AND GLUCOCORTICOIDS ON LUNG-FUNCTION OF PRETERM LAMBS

We asked whether a single-dose fetal treatment strategy using betameth asone plus either a long-acting beta(2) agonist (formoterol) or betame thasone plus agents that elevate intracellular cyclic adenosine monoph osphate (isobutyl methylxanthine and dibutyryl-cyclic adenosine monoph osphate) would augment the effects of prenatal betamethasone on postna tal lung function. Preterm lambs were treated with 0.5 mg/kg betametha sone or betamethasone plus the other agents and delivered 48 h after t reatment. The postnatal lung function as assessed by compliance, venti latory efficiency, and lung volumes at 40 min of age was improved by p renatal betamethasone and improved further by combination treatment, a lthough the augmented responses were not significantly greater than wi th betamethasone alone. Fatty acid synthase protein and enzymatic acti vity were not increased by betamethasone or combined treatments, in co ntrast to responses reported for other animal models. There were no ef fects of glucocorticoids or the combined treatments on surfactant. Sti mulation of the beta(2) agonist system did not augment postnatal lung function significantly above that noted for betamethasone alone with t he agents, doses, and duration of exposures tested.