The Effect of Parathyroid Hormone and Atrial Natriuretic Peptide on Cyclic Nucleotides Production and Proliferation of Avian Epiphyseal Growth Plate Chondroprogenitor Cells*

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Abstract
Cells derived from avian tibia epiphyseal growth plate were cultured in vitro. The cells which exhibited a polygonal phenotype and are termed chrondroprogenitor cells, developed in culture as a monolayer with a doubling time of 40-48 h in 5% fetal calf serum. Production of cAMP by the chondroprogenitor cells was stimulated by human (1-34) and bovine native (1-84) PTH. The effect of PTH on cAMP production could be blocked by the (3-34) PTH analog, suggesting interaction with specific receptors. cAMP production by avian chrondroprogenitor cells was also stimulated by cholera toxin, forskolin, and prostaglandin E2 but not by ACTH or prostaglandin F2.alpha.. PTH, cholera toxin, and forskolin also stimulated proliferation of the chondroprogenitor cells. In contrast, neither cAMP production nor proliferation of avian skin fibroblasts was affected by PTH. Human (1-28) and rat (5-28) atrial natriuretic peptide stimulated cGMP production by avian chrondroprogenitor cells and also by skin fibroblasts. Atrial natriuretic peptide inhibited the basal and PTH-stimulated [3H]thymidine incorporation into DNA of chondroprogenitor cells, but did not affect avian skin fibroblast proliferation. These results suggest that the proliferation of avian epiphyseal growth plate chondroprogenitor cells is modulated by opposing mechanisms induced by PTH and ANP, probably mediated by cAMP and cGMP, respectively.