Supraphysiological concentrations of dexamethasone induce elevation of calcium uptake and depression of [3H]-thymidine incorporation into DNA in cartilage in vitro.

When condylar cartilages of neonatal mice are treated in vitro with dexamethasone they respond with a significant depression of DNA synthesis. Concomitant with the retardative effect upon the incorporation of [3H]-thymidine, dexamethasone enhances the uptake of 45Ca by the condylar tissue. The hormone's effect upon calcium uptake is relatively rapid and takes place within 2 hours whereas the effect upon the incorporation of [3H]-thymidine takes place after a lag period of 24 hours. The present findings tend to indicate the casual relationship between the above effects of dexamethasone in fast growing cartilage. Further, there is evidence that both of the above responses are specific and are protein and mRNA synthesis dependent. Control studies using both a calcium ionophore (A23187) and a calcium blocker (D-600) provided data that further substantiate the proposed association among dexamethasone, calcium metabolism, and DNA synthesis in neonatal growth cartilage.