Brief perinatal hypoxia impairs postnatal development of the bronchiolar epithelium

We placed pregnant rats in 10% O2 on the last day of gestation for less than or equal to 9 h plus 1-2 h (with their pups) after the onset of delivery. In the pups this brief perinatal hypoxia led to an altered cellular composition of the bronchiolar epithelium that persisted at least to age 30 days; it was characterized by a higher nuclear numerical density (Nvn) of Clara cells, a lower Nvn of ciliated cells, and a lower percentage and Nvn of Clara cells in mitoses compared with control rats. The perinatal hypoxia also led to a significantly lower volume and volume density of the secretory apparatus (rough endoplasmic reticulum and secretory granules) on day 7 in 10% O2-born rats. The data on the Nvn of Clara and ciliated cells and on Clara cell mitoses are consistent with the notion that exposure to 10% O2 impaired the differentiation of Clara cells into ciliated cells and this impairment persisted well beyond the period of exposure.