(MI). MKK3-null mice were subjected to permanent coronaryartery ligation. Twenty-eight days after MI haemodynamics inmale mkk3+/+ (WT) and mkk3−/− (KO) littermates wereassessed using a pressure–conductance catheter, and planometryfollowing excision. MI groups were compared to un-operatedtime-matched WT and KO controls.

MI caused significant LV contractile dysfunction anddilatation which did not differ by genotype. Detailed morpho-metric analysis of excised hearts confirmed these similar globalindices of remodeling and also demonstrated that pathologicalchanges within remote myocardium and scar did not differbetween KO and WT hearts.

Despite numerous lines of evidence suggesting MKK3 is therelevant kinase upstream of p38 mitogen-activated proteinkinase in LV remodeling and heart failure these processes cancontinue in its absence.

Keywords: Cardiac remodeling; Signal transduction; Ventricu-lar function

doi:10.1016/j.yjmcc.2007.03.149

Prostanoid F receptor (FPR) inotropic effect in ratventricle is mediated by myosin light chain phosphorylationJ. Riise, C. Nguyen, E. Qvigstad, D. Sandnes, H. Eikemo,J.-B. Osnes, T. Skomedal, F.O. Levy, K.A. Krobert. Dept.Pharmacol., Univ. Oslo, Norway

In rat ventricle, activation of the Gq/11-coupled FPR increasescontractility and formation of inositol (1,4,5) trisphosphate (IP3)and diacylglycerol.

Objectives: 1) Determine if the FPR inotropic effect ismediated by increased phosphorylation of myosin lightchain-2 (MLC-2). 2) Elucidate the signaling pathway(s)activated by FPRs to regulate the phosphorylation state ofMLC-2. Contractility was measured in ventricular strips fromadult male Wistar rats. Strips were also snap frozen and thephosphorylation of both MLC-2 and myosin phosphatasetargeting subunit-2 (MYPT-2) was quantified. Stimulation ofthe FPR with fluprostenol increased contractility by ∼100%above basal and increased both MLC-2 (by ∼30%) andMYPT-2 (by ∼50%) phosphorylation. The myosin lightchain kinase (MLCK) inhibitor ML-7 and an inhibitor of Ca2+/calmodulin (W-7), the primary activator of MLCK, reducedboth the FPR inotropic effect and MLC-2 phosphorylation (by∼70% and ∼40%, respectively). Inhibition of Rho-kinase byY-27632 reduced the FPR inotropic effect and MLC-2phosphorylation by ∼45%. ML-7 and Y-27632 togetherreduced contractility by ∼82%. The FPR inotropic effectwas modestly reduced by IP3 receptor blockade (2-APB; by∼25%), but not by PKC inhibition (BIM). In conclusion, theFPR inotropic effect is mediated by increasing phosphoryla-tion of MLC-2 through regulation of both MLCK and myosinphosphatase activity. IP3-mediated Ca2+ release may beinvolved in the FPR inotropic effect but PKC is not. There-fore, FPR signaling mechanism(s) regulating MLC-2 phospho-

rylation likely extend beyond those currently established forGqα/11-coupled receptors.

Keywords: Signal transduction; Contractile proteins; Myosinheavy chain

doi:10.1016/j.yjmcc.2007.03.150

Cardioprotection from GSK-3β inhibition requiresactivation of PI-3 kinase and Src but not Akt, PKC,or ERKThomas Krieg, Heike Richter, Atsushi Kuno, Karina Förster,Stephan Felix. University Greifswald, Germany

Inhibition of glycogen synthase kinase-3β (GSK-3β) atonset of reperfusion is a key event in the protection ofpreconditioning. To determine GSK-3β's position in thesignal cascade we tested whether protection from itsinhibition with SB216763 (SB) requires activation of otherkinases including PI-3 kinase (PI3K), Src, Akt, protein kinaseC (PKC), and extracellular signal-regulated kinases (ERK). Inisolated rabbit hearts with 30-min regional ischemia/2-hreperfusion SB (1 μM) at reperfusion reduced infarctionfrom 38.5±3.7% of the risk zone in control hearts to 9.9±1.6%. Co-infusion of either PI3K blocker wortmannin or PP2, aselective Src inhibitor, aborted the protective effects (29.5±4.0% and 30.4±1.6% infarction, respectively). In contrast,inhibitors of PKC, ERK 1/2, Akt or blockade of adenosinereceptors were unable to block SB-induced protection indicatingupstream locations of these kinases and receptors. SB increasedAkt but not ERK1/2 phosphorylation. Thus Akt serves as areporter for PI3K but does not participate in protection fromdirect GSK-3β inhibition. Isolated adult ventricular rat myo-cytes were infected with adenovirus containing dominant-negative (dn) GSK-3β plasmid. Cells were loaded with TMREand exposed to H2O2 (100 μM) for 40 min. Fluorescence inten-sity was reduced compared to untreated cells (99.4±20.5 vs.292.6±22.4 a.u.) suggesting oxidant injury opened mitochon-drial permeability transition pores, while dnGSK-transfectedcells were protected (237.2±29.7 a.u.). dnGSK-transfected cellshad increased Akt phosphorylation. Therefore GSK-3β is pro-tective in hearts and isolated myocytes. PI3K and Src are re-quired downstream components in GSK-3β's protection, whileAkt, ERK 1/2, and PKC are not.

Keywords: Preconditioning; Signal transduction

doi:10.1016/j.yjmcc.2007.03.151

Opening of the mitochondrial KATP channel decreases JNKactivity in the anoxic-reoxygenated embryonic heartAlexandre Sarre, Stéphany Gardier, Fabienne Maurer,Christophe Bonny, Eric Raddatz. University of Lausanne,Switzerland

S53ABSTRACTS / Journal of Molecular and Cellular Cardiology 42 (2007) S37–S54