PROTEIN-KINASE-C (PKC)-MEDIATED PROTEIN-PHOSPHORYLATION IN RAT AORTIC SMOOTH-MUSCLE CELLS IS ENHANCED BY ALLYLAMINE

The profile of endogenous protein phosphorylation mediated by protein kinase C (PKC) was examined in cell fractions prepared from subcultured aortic smooth muscle cells (SMCs) isolated from rats treated with 70 mg/kg allylamine (AAM) or tap water for 20 days. Increased phosphorylation of endogenous proteins was observed under unstimulated conditions in the particulate, but not cytosolic, fraction of cells from AAM-treated animals (i.e. AAM cells) relative to control cells. Although the same phosphorylation bands were observed in the particulate or cytosolic fraction of control and AAM cells following phorbol ester stimulation of the enzyme, enhanced PKC-mediated phosphorylation was observed in both fractions of AAM cells relative to control cells. Measurements of exogenous histone Type III-S phosphorylation by PKC following in vitro exposure of naive SMCs to 100 mu M AAM for up to 60 min revealed that AAM selectively increased histone phosphorylation in the cytosolic fraction of SMCs. These results demonstrate that AAM treatment enhances PKC-mediated protein phosphorylation in rat aortic SMCs and raise the possibility that such alterations participate in the angiotoxic response to AAM.