Breakdown and release of myofilament proteins during ischemia and ischemia/reperfusion in rat hearts identification of degradation products and effects on the pCa-force relation

Jennifer E. Van Eyk, Francis Powers, William Law, Catherine Larue, Robert S. Hodges, R. John Solaro

Research output: Contribution to journalArticlepeer-review

Abstract

Our objective in experiments reported here was to identify myofilament proteins of rat hearts either lost or degraded by cardiac ischemia (15- or 60-minute duration) with and without 45 minutes of reperfusion. We correlated these changes with alterations in myofilament sensitivity to Ca2+ and maximum force generation. Protein degradation and loss were assessed by high- performance liquid chromatography, SDS-PAGE, Western blotting analysis, and amino acid sequencing. Compared with nonischemic control hearts, bundles of skinned fibers from hearts subjected to ischemia alone demonstrated a decrease in maximum force generation and an increase in sensitivity to Ca2+. These changes in function were increased with the duration of the ischemia and with reperfusion. With increasing duration of ischemia, there was an increased loss and degradation of myofibrillar α-actinin and troponin I (TnI) at its C-terminus. α-Actinin and TnI were most susceptible to ischemia, but with 60 minutes of ischemia/reperfusion, there was also degradation of myosin light chain-1 (MLC1) involving a clip of residues 1 to 19. The MLC1 degradation product was detected in the reperfusion effluent (along with troponin T, tropomyosin, and α-actinin) but not in the tissue with 60 minutes of ischemia with no reperfusion. Moreover, with ischemia the following proteins became associated with the myofibrils: GAPDH and proteins of the mitochondrial ATP synthase complex. Our results provide new evidence regarding the mechanism by which ischemia/reperfusion causes myocardial injury and support the hypothesis that an important element in the injury is altered activity and structure of the myofilaments.

Original languageEnglish (US)
Pages (from-to)261-271
Number of pages11
JournalCirculation research
Volume82
Issue number2
DOIs
StatePublished - Feb 9 1998

Keywords

  • Myocardial ischemia/reperfusion
  • Myofilament
  • Protein degradation
  • Troponin I
  • α-actinin

ASJC Scopus subject areas

  • Physiology
  • Cardiology and Cardiovascular Medicine

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