Studies on hormonal regulation of the growth of the craniofacial skeleton: IV. Specific binding sites for glucocorticoids in condylar cartilage and their involvement in the biological effects of glucocorticoids on cartilage cell growth.

Using a whole-tissue binding assay and cell-free binding measurements indicated the presence of a specific steroid receptor for triamcinolone in cartilage cells of neonatal mouse mandibular condyle. Analysis of receptor levels showed that whole-tissue preparations bound 1360 fmol triamcinolone/mg protein. Affinity measurements revealed a dissociation constant of 7.6 X 10(-9) M. There was a close correlation between triamcinolone inhibition of DNA synthesis and steroid occupancy of whole-tissue receptors. The inhibitory effect of triamcinolone upon DNA synthesis could be significantly reduced by "blocking" the respective receptors with cortexolone. All the cartilage cells in the condyle revealed distinct intracellular labeling using [3H] dexamethasone autoradiography. Hence, neonatal condylar cartilage, an active site of endochondral bone formation in the craniofacial skeleton, can be regarded as a genuine target tissue for the biological effects of glucocorticoids.