Expression of activated PKC epsilon (PKC epsilon) protects the ischemic heart, without attenuating ischemic H(+) production

Abstract

PKC epsilon is a PKC isoform that translocates during preconditioning and may mediate cardioprotection. To investigate whether PKC epsilon activation is cardioprotective, Langendorff-perfused hearts from wild-type (WT) mice and from mice expressing constitutively active mutant PKC epsilon were subjected to 20 min ischemia and 40 min reperfusion while(31)P NMR spectra were acquired. Pre-ischemic glycogen levels were similar in WT and PKC epsilon hearts. During ischemia, ATP fell less in PKC epsilon than in WT hearts. Ischemic intracellular pH, however, was similar in WT and PKC epsilon hearts. During reperfusion, recovery of contractile function and ATP were greater in PKC epsilon than WT hearts. In conclusion, expression of activated PKC epsilon protected hearts from post-ischemic energetic and contractile dysfunction, consistent with the proposed cardioprotective role of PKC epsilon. Protection occurred in the PKC epsilon hearts without attenuation of ischemic H(+) production, implying that, at least in this ischemic model, reduced acidification during ischemia is not necessary for cardioprotection.