Gestational changes in the level of glucocorticoid-binding sites in fetal bovine cartilaginous tissues

In order to assess glucocorticoid actions on fetal cartilage development, [3H]dexamethasone binding site levels in fetal bovine cartilaginous tissues from long bones were measured, using a whole cell assay at 37 degrees C. Displaceable [3H]dexamethasone binding in epiphysial growth cartilage was maximal (16.2 fmol/10(6) cells) in fetuses of 10-15 cm crown-rump length (CR), and declined to 22% of the maximum in fetuses of 20-30 cm CR. Subsequently, [3H]dexamethasone binding rose to a plateau (13.0 fmol/10(6) cells) in fetuses of 30-80 cm CR and declined in those of 80-100 cm CR. When measured in growth plate cartilage, [3H]dexamethasone binding was significantly higher in fetuses of 40-80 cm CR (39 fmol/10(6) cells) than in those of 80-100 cm CR. There was no significant change of [3H]dexamethasone binding affinities in epiphysial chondrocytes of 5-100 cm CR fetuses or in growth plate chondrocytes of 40-100 cm CR fetuses. These results demonstrate that fetal cartilaginous tissues during development possess varying cellular levels of glucocorticoid binding and may thus have temporal changes in sensitivity to glucocorticoid hormones.