Receptor-mediated glucocorticoid inhibition of cell proliferation in mouse growth cartilage in vitro

The growth hormone of neonatal facial cartilage from ICR mice is inhibited by glucocorticoid treatment in vitro. A reduction of the overall tissue weight is accompanied by a substantial decrease in the protein content of the tissue. For the first 48 h in culture, hormone-treated cartilage undergoes a complete standstill in protein gain, and only thereafter the protein content increases, yet is markedly smaller than that of control specimens. Further, a significant reduction in the DNA content is seen already by 24 h, a feature that intensifies by 48 h. A slight recovery takes place thereafter. The reduction in DNA concentration is accompanied by a significant decrease in [3H]thymidine incorporation in acid-insoluble material. The inhibition of DNA synthesis by triamcinolone acetonide is protein- and RNA-synthesis-dependent. Autoradiographic examinations reveal that young cartilage cells are heavily labelled with [3H]dexamethasone and that this labelling is specific. To further substantiate the involvement of glucocorticoid-specific receptors in the latter's inhibitory effects, tissues were treated with cortexolone, this apparently 'masking' the cytosolic receptors for glucocorticoids, and thereby succeeded to eliminate the growth-inhibitory effect of triamcinolone. These results provide evidence for a receptor-mediated set of responses to glucocorticoids in these cartilage cells.