322 Prenatal Glucocorticoids: Effects on Lung of Newborn Rats Exposed to Hypoxia and Recovered in Hyperoxia or Air.

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Aims: To examine the morphometric changes produced on lung of neonatal rats treated with prenatal administration of betamethasone or dexamethasone, and test the hypothesis if glucocorticoids would produce any difference when pups are exposed to hypoxia and its recovery with oxygen or air ambient. Material and Methods: Dexamethasone, Bethametasone or equivalent saline solution was administered i.v. To gestant Wistar rats on 20 and 21 day of gestation. All rats delivered their pups within 48 hours after the last injection. The groups of rat pups were randomly assigned to either. At 4–8 hours of life newborn rats were exposed in sequential way during 2 hours in hypoxia, and recovered in > 95% oxygen or 21% oxygen. Lung and body weight were measured. For the morphometric study the lungs were fixed by intratracheal instilation of formol at a pressure of 20 cm.H2O. Quantitative morphometric assessment was done on coded slides with 400x magnification and a eye piece with a sample square grid pattern (model CPLW 1018, Zeiss Optical, Hannover Md). Morphmetric changes are shown in table 1. Statystical Analyses: ANOVA test was performed followed by Bonferroni test. P< 0,05 was considered. Result: Comparative wet lung weight/dry lung weight and morphometric study is show in table I DEX (dexamethasone) BETA (bethametasone) W.(weight), Sa (alveolar surface), SV (surface density of alveolar walls), Nv (numerical density of alveoli), rv (alveolar radius) * Significant differences with saline group. Conclusion: Prenatal administration of dexametasone and bethametasone causes a reduction in alveolar number in newborn rats. Lungs of treated pups showed a longer alveoli radius, lower values of surface density of alveolar walls and lower numerical density of alveoli than the control group. Probably, prenatal glucocorticoids could produce a partial suppression of the formation of secondary septa and decreased final alveoli number.