MDL-28170, a membrane-permeant calpain inhibitor, attenuates stunning and PKC(ε) proteolysis in reperfused ferret hearts

Academic Article

Abstract

  • Objectives: This paper tests the hypothesis that calpains are activated in the ischemic (I)/reperfused (R) heart and contribute to myocardial stunning. Methods: Isolated ferret hearts were Langendorff perfused isovolumically, and subjected to 20 min of global I followed by 30 min of R in the presence or absence of 0.2 μM MDL-28170, a membrane-permeant calpain inhibitor. Right trabeculae then were isolated from these hearts, skinned chemically, and pCa2+-force curves obtained. Samples of left ventricle were extracted, subjected to SDS-PAGE, and Western analyzed for PKC(ε) and PKM(ε). Results: Perfused ferret hearts exhibit a 43% decline in left ventricular developed pressure during R. Pre-treatment of hearts with MDL- 28170 prior to I significantly improves function during R. Trabecular myofilaments from normal hearts have a K(D) for Ca2+ of 6.27 ± 0.06; I/R decreased the K(D) to 6.09 ± 0.04; trabeculae from I/R hearts pre-treated with MDL-28170 have a K(D) of 6.28 ± 0.04. Western analysis shows ferret hearts to contain a single ≃ 96 kDa species of PKC(ε). I/R hearts contain the native PKC(ε) and a ≃ 25 kDa smaller species of PKC(ε), which corresponds to PKM(ε), the calpain proteolyzed form of PKC(ε). Pre- treatment of I/R hearts with MDL-28170 markedly diminishes PKM(ε) in reperfused hearts. Conclusions: Mechanical stunning during R is sensitive to MDL-28170. Depressed mechanical function is reflected in a hyposensitization of trabecular myofilaments to Ca2+. Western analysis shows that PKM(ε) is present in R hearts.
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    Author List

  • Urthaler F; Wolkowicz PE; Digerness SB; Harris KD; Walker AA
  • Start Page

  • 60
  • End Page

  • 67
  • Volume

  • 35
  • Issue

  • 1