Abstract: Partially purified protein kinase C and protein kinase A were separately incubatedwith various concentrations of PDS(1～1000μg·mL^-1)for l0 min in vitro. The results indicate thatprotein kinase C activity was inhibited in a dose-dependent manner by PDS, but typeⅠand typeⅡprotein kinase A were not.In cardiomyocytes preincubated with PDS( 250,500,1000μg· mL^-1) for 10 min,PMA-induced decrease of cytosol protein kinase C activity and increase of membrane protein kinase CactiVity were greatly inhibited in the same manner. These results suggest that PDS not only inhibitedprotein kinase C in vitro, but also inhibited activation of protein kinase C in cardiomyocytes.