Induction of c-fos mRNA in rat lymphoma Nb-2 cells

Cyclosporin A, immunosuppressive agent, reversibly blocks the mitogenic effect of prolactin in rat lymphoma Nb-2 cells and removal from the medium leads to a rapid and transient induction of c-fos mRNA. Activators of protein kinase C, such as TPA, mellitin and phospholipase C and the calcium ionophore, A23187, induced c-fos mRNA in the presence or absence of cyclosporin A. Activators of the cAMP pathway such as forskolin, dBcAMP and cholera toxin failed to induce c-fos mRNA in the presence or absence of cyclosporin A. These results suggest that cyclosporin A may act at the level of protein kinase C.