The presence in bovine trachealis muscle of cytosol receptors with high affinity for glucocorticoids

Whereas receptors with high affinity for glucocorticoids have been reported present in both fetal and adult lungs, there has been no attempt to identify such receptors in airways smooth muscle. We have examined the binding characteristics of glucocorticoids for a cytosol fraction prepared from bovine trachealis muscle. The cytosol fraction, which was prepared in 10 mM Tris, 1.5 mM Na₂ EDTA and 2 mM dithiothreitol, contained macromolecular high affinity receptors for ³H-dexamethasone (Kd = 5.6 nM) at a concentration of 0.20 pmol/mg protein. The comparative affinities of other steroids in descending order were: beclomethasone-17,21-dipropionate, dexamethasone, betamethasone, triamcinolone and triamcinolone acetonide. Progesterone and deoxycorticosterone only bound to a limited extent, whereas the binding with 5α-dihydrotesterone and pregnenolone was negligible. We conclude that airways smooth muscle is a target tissue for glucocorticoids and postulate that the binding of glucocorticoids to these receptors may represent the initial step in the anti-asthmatic action of these drugs.