Effects of Acute Hyperoxia on Hyaluronic Acid and Histopathology of the Lung in Neonatal Ratst

Abstract

We studied the effects of hyperoxia()95% oxygen for 10 days) on changes in body weight, changes in wet to dry lung weight ratio, changes in hyaluronic acid of the lung, and morphologic changes in lung tissue compared with those of normoxia (room air for 10 days) in Sprague-Dawley neonatal rat pups. In this acute hyperoxic neonatal rat model, we tried to analyze the relationship of relative water content of the wet lung and the amount of hyaluronic acid and morphologic change in lung tissue. The results were as follows: 1) Increase of postnatal body weight among survivors was stunted significantly under hyperoxia compared with normoxia during 10 days-experiment. 2) No appreciable difference of wet to dry lung weight ratio was noted on the beginning and the tenth day of experiment in neonatal rat pups between normoxia and hyperoxia, but considerable increased wet to dry lung weight ratio was noted significantly at 5, 7 days of hyperoxia suggesting that the relative water content of the wet lung was increased on the fifth, seventh day of experiment in hyperoxia compared with normoxia, 3) The amount of hyaluronic acid per wet lung decreased sequentially according to increase of postnatal age in normoxia, but a considerably increased amount of hyaluronic acid per wet lung was noted significantly on the fifth, the seventh day of experiment in hyperoxia. The difference in amount of hyaluronic acid per wet lung was not significant on the tenth day of experiment between normoxia and hyperoxia. These results suggested that the changing pattern of amount of hyaluronic acid per wet lung coincided with that of the relative water content of the wet lung in hyperoxia. 4) Pulmonary edema, interstitial inflammatory cell hypercellularity, and localization of hyaluronic acid in interstitial lung lesion were observed by light microscope at 7 days of exposure in hyperoxia compared with normoxia. These results suggest the possible role of hyaluronic acid on increase of water content and interstitial inflammatory cells in acute lung injury due to hyperoxia in an experimental neonatal rat model.