POSSIBLE ROLE OF TYROSINE KINASES IN THE PROLACTIN STIMULATION OF CELL-DIVISION IN NB2 NODE LYMPHOMA-CELLS

Orthovanadate and genistein were employed to determine the possible ro le of tyrosine kinase in the prolactin stimulation of cell division in Nb2 node lymphoma cells. Orthovanadate (0.1-0.25 muM), an inhibitor o f specific phosphatases, was found to stimulate cell division as well as potentiate the mitogenic effect of prolactin on Nb2 cells when prol actin was employed at a less than maximum stimulatory concentration. G enistein, an inhibitor of tyrosine kinase, was found to inhibit the pr olactin stimulation of cell division. Since prolactin was shown in ear lier studies to stimulate the phosphorylation of tyrosyl residues in s pecific Nb2 cell proteins, these results suggest that the signal trans duction pathway for the prolactin stimulation of cell division in the Nb2 node lymphoma cells likely involves the participation of tyrosine kinase(s).