PTH STIMULATES THE PROLIFERATION OF TE-85 HUMAN OSTEOSARCOMA CELLS BY A MECHANISM NOT INVOLVING EITHER INCREASED CAMP OR INCREASED SECRETION OF IGF-I, IGF-II OR TGF-BETA

Injections of parathyroid hormone (PTH) result in increased bone formation in several species. Work in our laboratory and others has shown a stimulation of bone cell proliferation and growth factor production by PTH. Our purpose was to study the effects of PTH on a human bone cell line using TE-85 human osteosarcoma cells as a model. After 24 h treatment, PTH caused an increase in cell proliferation as measured by cell counts and [H-3]-thymidine incorporation. Proliferation was not inhibited by an anti-transforming growth factor beta (TGF-beta) antibody which could abolish stimulation by exogenous TGF-beta. PTH did not stimulate cAMP production, alkaline phosphatase activity or production of insulin-like growth factors I or II (IGF-I or IGF-II) in TE-85 cells. Although basal TE-85 proliferation was slowed by incubation with the calcium channel blocking agent verapamil, PTH still caused an increase in growth rate. We conclude that PTH directly stimulates TE-85 proliferation via a mechanism not involving increased adenylate cyclase activity or increased secretion of IGF-I, IGF-II or TGF-beta and may stimulate bone formation in vivo by activating some other mitogenic signal to increase bone cell proliferation.