Compartmentalization of 11-oxidoreductase within fetal lung alveolus.

The role of 11-oxidoreductase in the cellular process of fetal lung surfactant production and its localization within the alveolar domain have been investigated. In organotypic cultures of fetal rat lung, cortisol and cortisone markedly stimulate saturated phosphatidylcholine synthesis by the alveolar type II cell; a 10-fold excess of 11-ketoprogesterone blocks the bioactivity of cortisone. Both cortisol and cortisone also stimulate fibroblast-pneumonocyte factor production, whereas 11-ketoprogesterone blocks the effect of cortisone, but not of cortisol, suggesting that cortisone stimulation of fibroblast-pneumonocyte factor production depends on its conversion to cortisol by 11-oxidoreductase. A survey of the cells that are present in the alveolar domain revealed that 11-oxidoreductase activity is only present in the fibroblast. Localization of both 11-oxidoreductase and fibroblast-pneumonocyte factor production within the same cell emphasizes the significance of 11-oxidoreductase in the regulation of fetal lung surfactant production.