α and β glucocorticoid receptor mRNA expressionin skeletal muscle

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Abstract

Summary

The aim of the present study was to investigate the occurrence and autoregulation of both glucocorticoid receptor mRNAs in rat gastrocnemius muscle. The expression of both receptor forms was studied 1, 4 or 12hours after intra-tracheal instillation of a high dose (100μg) of budesonide; muscular expression was compared with glucocorticoid receptor expression in lung tissue. After Northern blot analysis, hybridization was performed with glucocorticoid receptor, glyceraldehyde-3-phosphate dehydrogenase and glutamine synthetase probes. In the gastrocnemius muscle, both the α and β glucocorticoid receptor mRNA forms were detected and found to be downregulated four hours after the budesonide instillation. α/β glucocorticoid receptor ratios were lower in the gastrocnemius (1.1±0.2) than in the lungs (2.6±0.6). In the lungs, at all time points, the average α glucocorticoid receptor mRNA levels did not differ from controls, although glutamine synthetase mRNA levels were upregulated. The β glucocorticoid receptor mRNA was slightly reduced at 1 and 4hours. In conclusion, after intra-tracheal instillation of budesonide, both α and β glucocorticoid receptor forms were downregulated in muscle tissue. The difference in α/β glucocorticoid receptor mRNA ratios and concentrations between lung and gastrocnemius muscle supports the hypothesis of differential gene regulation by glucocorticoids in different cell types.

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