Selective activation of diaphyseal chondrocytes by parathyroid hormone, calcitonin and N6,O2-dibutyryl adenosine 3',5'-cyclic monophosphoric acid in proteoglycan synthesis of chick embryonic femur cultivated in vitro.

We have found that the developmental stage of chondrocytes in the chick embryo femur is sensitive to the action of PTH, CT and dibutyryl cyclic AMP in stimulating proteoglycan synthesis as estimated by the incorporation of radioactive inorganic sulfate. PTH treatment of the cartilage resulted in dramatic stimulation of the proteoglycan synthesis in the diaphysis, which is composed of rather old non-dividing hypertrophied chondrocytes with much lower proteoglycan-synthesizing activity than younger dividing cells in the epiphysis and metaphysis. No or slight stimulation was observed the epiphysis and metaphysis. Dibutyryl cyclic AMP produced much the same effect. CT also stimulated the proteoglycan synthesis only in the diaphysis but the stimulation was less potent (133% of control) than PTH (650% of control) or dibutyryl cyclic AMP (625% of control). The hormones and dibutyryl cyclic AMP, therefore, seem to activate the proteoglycan synthesis specifically in rather old chondrocytes of the diaphysis. A synergistic effect of PTH and CT suggesting a different stimulating mechanism was observed in the diaphysis.