TRANSLOCATION OF PROTEIN-KINASE C-ALPHA, C-DELTA AND C-EPSILON ISOFORMS IN ISCHEMIC RAT-HEART

To explore the spatial and temporal localization of PKC isoforms durin g ischemia, we quantified PKC isoforms in the subcellular fractions in perfused rat heart by immunoblotting using specific antibodies agains t PKC isoforms. PKCs-alpha and epsilon translocated from the 100 000 X g supernatant (S, cytosolic) fraction to the 1000 x g pellet (P1, nuc leus-myofibril) and the 1000-100 000 X g pellet (P2, membrane) fractio ns during 5-40 min of ischemia. PKC-delta redistributed from the P2 to the S fraction. A 50-kDa fragment of PKC-cu appeared during ischemia possibly through calpain action. Immunohistochemical observations show ed the different localizations of PKC-alpha, delta, and epsilon in the myocytes. The PKC assay displayed high basal levels of Ca2+-independe nt PKC, the activation of Ca2+-dependent PKC in the P1 and P2 fraction s, and the activation of Ca2+-independent PKC in the P1 fraction after 20 min of ischemia.