title: Dexamethasone and 8-bromo-cyclic AMP depress the incorporation of [3H]thymidine into mouse condylar cartilage by different pathways.
abstract: We examined whether cyclic AMP (cAMP) affects the incorporation of [3H]thymidine into cartilage cells and, if so, whether this action could be related to the inhibitory effect of glucocorticoid hormones on the growth of ossifying cartilage. Incorporation of [3H]thymidine into trichloroacetic acid-precipitable material by mouse cartilage was measured concomitantly with the concentration of cAMP. Dexamethasone (1 mumol/l) significantly (P less than 0.05) depressed the incorporation of [3H]thymidine. The cAMP analogue 8-bromo-cAMP (0.01-1 mmol/l) also depressed the incorporation of the radionucleotide in a dose-dependent fashion. When various concentrations of 8-bromo-cAMP were added with dexamethasone (1 mumol/l), no apparent changes took place compared with the effect of dexamethasone alone. The phosphodiesterase inhibitor 3-isobutyl-1-methylxanthine (0.2-1 mmol/l) elicited an inhibitory effect on [3H]thymidine incorporation and a stimulatory influence on cartilage cAMP concentrations. Dexamethasone, at doses (0.01-1 mumol/l) causing significant inhibition of [3H]thymidine incorporation, failed to increase cartilage levels of cAMP. It seems, therefore, that the depressive effect of dexamethasone on [3H]thymidine incorporation in condylar cartilage is not mediated through an increase of cAMP in the tissue.
mesh_terms: D015124:8-Bromo Cyclic Adenosine Monophosphate / Q000494:pharmacology*; D000818:Animals; D002356:Cartilage / Q000187:drug effects / Q000378:metabolism*; D000242:Cyclic AMP / Q000378:metabolism; D003864:Depression, Chemical; D003907:Dexamethasone / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D051379:Mice; D008815:Mice, Inbred Strains; D013936:Thymidine / Q000378:metabolism*
chemical_list: D015124:8-Bromo Cyclic Adenosine Monophosphate; D003907:Dexamethasone; D000242:Cyclic AMP; D013936:Thymidine