Protein kinase C expression and subcellular distribution in chronic myocardial ischemia. Comparison of two different canine models

We studied protein kinase C (PKC) isozyme expression and activity distribut ion in two models of chronically ischemic canine myocardium: (1) single ves sel obstruction (SVO), produced by tight stenosis of LAD followed by precon ditioning and acute ischemia (40 min); (2) three vessel obstruction (3VO), produced by LAD-stenosis and gradual occlusion of right coronary artery and left circumflex. In both models after 8 weeks of chronic ischemia the dogs were either sacrificed or had PTCA of the LAD with a follow up of another 4 weeks. Control dogs were sham operated. PKC activity was measured in subc ellular fractions of tissue samples from anterior and posterior regions in the presence of histone and gamma-[P-32]-ATP. PKC isozymes were detected by Western blotting. All regions perfused by the obstructed coronaries were d ysfunctional at 8 weeks when compared to baseline, with improvement of ante rior wall function after PTCA of LAD. PKC activity was elevated in the memb rane fraction of SVO, but unchanged in the 3VO model. PKCs alpha, epsilon, and zeta prevailed in cytosol fraction of the controls (cytosol/membrane ra tios were +/- 3.34, 1.38 and 4.56 for alpha, epsilon and zeta, respectively ), consistent with PKC activity distribution, while delta was not detected. There was no significant difference between the groups concerning the rela tive membrane amount of the isozymes. PKCs alpha and epsilon were decreased in the cytosol fraction of both models at 8 weeks (for anterior region, by 56 and 57% in SVO and by 49 and 46% in 3VO, respectively) without there be ing any differences between anterior and posterior regions, and were low al so in the PTCA group. PKC zeta distribution however varied between the two models. The amount of PKC zeta isozyme was downregulated by 45% after 8 wee ks of chronic ischemia and returned towards the control values after PTCA i n the anterior region of SVO, while it did not change in anterior wall afte r 8 weeks in 3VO but was significantly decreased (by 47%) in posterior regi on after PTCA. In conclusion, our results suggest modified PKC signalling i n chronically ischemic canine myocardium.