syntide-2 and Myocardial-Ischemia

The signal transduction pathways that mediate the cardioprotective effects of ischemic preconditioning remain unclear. Here we have determined the role of a novel kinase, protein kinase D (PKD), in mediating preconditioning in the rat heart. Isolated rat hearts (n=6/group) were subjected to either: (i) 36 min aerobic perfusion (control); (ii) 20 min aerobic perfusion plus 3 min no-flow ischemia, 3 min reperfusion, 5 min no-flow ischemia, 5 min reperfusion (ischemic preconditioning); (iii) 20 min aerobic perfusion plus 200 nmol/l phorbol 12-myristate 13-acetate (PMA) given as a substitute for ischemic preconditioning. The left ventricle then was excised, homogenized and PKD immunoprecipitated from the homogenate. Activity of the purified kinase was determined following bincubation with [gamma32P]-ATP+/-syntide-2, a substrate for PKD. Significant PKD autophosphorylation and syntide-2 phosphorylation occurred in PMA-treated hearts, but not in control or preconditioned hearts. Additional studies confirmed that recovery of LVDP was greater and initiation of ischemic contracture and time-to-peak contracture were less, in ischemic preconditioned hearts compared with controls (P<0.05). Our results suggest that the early events that mediate ischemic preconditioning in the rat heart occur via a PKD-independent mechanism.

Topics: 3T3 Cells; Aerobiosis; Animals; Cells, Cultured; Enzyme Activation; Fibroblasts; Heart; Intercellular Signaling Peptides and Proteins; Ischemic Preconditioning, Myocardial; Male; Mice; Myocardial Ischemia; Myocardium; Peptides; Perfusion; Phosphorylation; Protein Kinase C; Protein Processing, Post-Translational; Protein Serine-Threonine Kinases; Rats; Rats, Wistar; Signal Transduction; Stimulation, Chemical; Subcellular Fractions; Tetradecanoylphorbol Acetate