Effect of cortisone on permeability of the neonatal rat lung to drugs.

The effect of cortisone (5 mg/animal i.p. on day 5 after birth) on the development of adult-type permeability characteristics in the lung was investigated in rats 6-18 days of age. In both treated and control rats, the lipid-soluble drug procainamide was absorbed at similar rates in all age groups. In contrast, in cortisone-treated animals, pulmonary absorption rates for the lipid-insoluble compounds mannitol and p-aminohippuric acid declined to adult levels at the age of 6 days, which was 12 days earlier than in controls. Cortisone treatment thus accelerates development of adult permeability characteristics in the pulmonary epithelium.