Detection of high-affinity glucocorticoid binding in rat bone.

Abstract

Department of Medicine, Manchester Royal Infirmary, Manchester, M13 9WL (Received 17 October 1977) Recently Feldman, Dziak, Koehler & Stern (1975) have detected high-affinity gluco corticoid receptors in cytosol from isolated foetal rat calvarial bone cells. They estimated the binding constant (Kd) to be 7×10−9 mol/l for [3H]dexame[unk]hasone; however, their estimates were based on a maximum bound: free ratio of only 1%. Their data from cell cultures suggest that such binding may nevertheless be of physiological importance (Chen, Aronow & Feldman, 1977). The very small amount of binding might be due to a low initial concentration of binding sites, to their destruction during or after the trypsin–collagenase digestion, to their high dilution or to a combination of all three factors. We report here a much simpler method whereby we have greatly increased the percentage binding by setting up the incubation in intact calvaria. Calvaría were dissected from foetal rats (19–21 days