Induction of early response genes by hypergravity in cultured mouse osteoblastic cells (MC3T3-E1).

Hypergravity as low as 50g transiently stimulated cultured mouse osteoblastic cells (MC3T3-E1) to induce early response genes such as c-fos and egr-1, whereas expression of c-jun was marginally affected. The maximum induction of c-fos required more than 90g, but egr-1 induction became maximum below 50g. Staurosporin inhibited the induction of c-fos by hypergravity almost completely at a concentration of 0.1 microM, but it inhibited the induction of egr-1 only partially. In cells pretreated with 12-O-tetradecanoylphorbol 13-acetate, induction of c-fos by hypergravity was almost completely abolished, whereas that of egr-1 was not affected. Activity of protein kinase C seemed to be activated in cells centrifuged at 900g. These results indicate that hypergravity stimulates multiple signal transduction cascades that are connected with the expression of early response genes.