REGULATION OF THE GLUCOCORTICOID RECEPTOR IN FETAL-RAT LUNG DURING DEVELOPMENT

The effect of the synthetic glucocorticoid betamethasone on the regulation of the glucocorticoid receptor mRNA and on receptor protein was studied in fetal rat lung during development. Using a glucocorticoid receptor cRNA probe, glucocorticoid receptor mRNA was examined by Northern blot hybridization and by solution hybridization. A monoclonal antibody against the glucocorticoid receptor was used to study regulation of the receptor protein by the Western immunoblotting technique. In fetal rat lungs, of 16-21 days of gestation, as well as in adult lungs, betamethasone treatment resulted in a significant decrease of glucocorticoid receptor mRNA to 50-65% of the control level. In contrast, betamethasone treatment did not down-regulate the receptor protein in rat lungs of 16-19 days of gestation, whereas a decrease of glucocorticoid receptor protein to 40-60% of control was seen in lungs of 21 days of gestation, in postnatal and adulting lung. These results provide data for a change in regulation in vivo of the glucocorticoid receptor by its homologous ligand in fetal rat lung during development.