ATP and adenosine act as a mitogen for osteoblast-like cells (MC3T3-E1).

Extracellular ATP, and to a lesser extent adenosine, an ATP metabolite, stimulated cell proliferation in osteoblast-like cells (MC3T3-E1). ATP increased cytosolic Ca2+ due to Ca2+ mobilization from intracellular storage in the same concentration range of the nucleotide as that effective for DNA synthesis, suggesting the mediation of the phospholipase C/Ca2+ system in the mitogenic action. Since adenosine induced no Ca2+ mobilization, P2-purinergic receptor appears to be associated with ATP actions. The growth-promoting effect of ATP was not inhibited by H7, a protein kinase C inhibitor, and indomethacin, a cyclooxygenase inhibitor, indicating no involvement of activation of protein kinase C and production of prostaglandins in ATP-induced mitogenic signals. Either ATP or adenosine remarkably and synergistically potentiated platelet derived growth factor-induced DNA synthesis. These findings suggest that extracellular ATP and adenosine may play a physiological role in the regulation of bone formation.