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

This study investigates the relationship between the rate of phorbol e ster-induced contraction of intact rat aorta and protein kinase C acti vation, 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+-induc ed protein kinase C translocation during tissue homogenization. Phorbo l myristate acetate, as well as phorbol dibutyrate, decreased cytosoli c 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 e ster-induced contraction of intact vascular smooth muscle is associate d in a time-dependent manner with protein kinase C activation.