INHIBITION OF PHYTOHEMAGGLUTININ-STIMULATED BOVINE MONONUCLEAR CELL-PROLIFERATION, INTERLEUKIN-2 PRODUCTION AND PROTEIN KINASE-C ACTIVITY BY A PROTEIN KINASE-C INHIBITOR, H-7

1-(5-Isoquinolinesulfonyl)-2-methylpiperazine dihydrochloride (H-7), a potent and selective inhibitor of protein kinase C (PKC), inhibited PHA-stimulated bovine peripheral blood mononuclear cell (PBMC) proliferation, interleukin-2 (IL-2) production, and cytosolic PKC activity without affecting the cell viabilities. Presence of exogenous cytokines, such as purified human IL-2 or recombinant bovine IL-2 (rbovIL-2), reversed the H-7 inhibitory effects on PHA-stimulated PBMC proliferation. We conclude that the PKC enzyme plays an important role as a second messenger in bovine PBMC proliferation in the early stages of cell activation. © 1990.