TIME-COURSE OF PHORBOL ESTER-INDUCED CONTRACTION AND PROTEIN-KINASE-C ACTIVATION IN RAT AORTA

This study investigates the relationship between the rate of phorbol ester-induced contraction of intact rat aorta and protein kinase C activation, as assessed by the translocation of protein kinase C from the cytosolic to the particulate fraction. Aorta was exposed to Ca2+-free physiologic salt solution prior to phorbol ester to prevent Ca2+-induced protein kinase C translocation during tissue homogenization. Phorbol myristate acetate, as well as phorbol dibutyrate, decreased cytosolic and/or increased particulate protein kinase C activity as early as 5 s following phorbol ester addition, which was prior to, or coincident with, the onset of contraction. These results suggests that phorbol ester-induced contraction of intact vascular smooth muscle is associated in a time-dependent manner with protein kinase C activation.