The Rabbit Fetal Lung as a Glucocorticoid Target Tissue1,2

Fetal lung cells from 28 day gestation rabbits cultured in the presence of cortisol (5.5 ×10−6M), corticosterone (5.5 × 10−6M) or dexamethasone (5.5 × 10−8M) incorporated [3H]choline into lecithin to a significantly greater extent than did control cultures. 11-Deoxycortisol, 21-deoxycortisol and ll)βhydroxyprogesi:erone, at a concentration of 5.5 × 10−5M, had no effect on lecithin synthesis. However, when lung cells were simultaneously exposed to these sterofds and to cortisol at the concentrations quoted, [3H]choline incorporation was reduced to control values. Cortisone (5.5 × 10−6M) also enhanced lecithin synthesis, the activity of the steroid likely being related to the capacity of the lung cells to convert cortisone to cortisol. This hypothesis was supported by the observations that 11-ketoprogesterone (1.3 × 10−5M), which totally inhibited the conversion of cortisone to cortisol and which had no effect of its own on [3H]choline incorporation, inhibited the effect of cortisone on lecithin synthesis b...