PKC-dependent delayed metabolic preconditioning is independent of transient MAPK activation

In this study we used an in vitro model of delayed preconditioning to inves tigate activation of mitogen-activated protein kinases (MAPKs) and their po tential role in protection. Neonatal rat cardiomyocytes were preconditioned using a buffer containing glycolytic inhibitors and low pH (minimal metabo lic preconditioning; MMPC) consisting of modified Krebs buffer, 10 mM 2-deo xy-glucose, and 20 mM lactate, pH 6.8, for 2 h followed by 24 h of simulate d reperfusion before lethal simulated ischemia (LSI). MAPK activation durin g the MMPC protocol was determined using phospho-specific antisera and the effect on protection determined following LSI. Rapid, transient phosphoryla tion of extracellular signal-regulated kinases 1 and 2 (ERK1/2) and p38 MAP K was observed during each of the MMPC, reperfusion, and LSI phases; an eff ect blocked by MAPK inhibitors PD-98059 and SB-203580, respectively, but no t by the protein kinase C (PKC) inhibitor Ro31-8220. However, although MMPC was blocked by Ro31-8220, treatment with the MAPK inhibitors during the pr econditioning protocol did not block delayed protection conferred by MMPC. Thus the data suggest that, in this model of delayed preconditioning, prote ction appears to be PKC dependent but independent of ERK1/2 or p38 MAPK act ivation.