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Reduced cardiac myofibrillar Mg-ATPase activity without changes in myosin isozymes in patients with end-stage heart

A A Alousi1, A M Grant, J R Etzler

  • 1Sterling Research Group, Rensselaer, NY.

Molecular and Cellular Biochemistry
|July 17, 1990
PubMed

Insights

Reduced myofibrillar ATPase activity in end-stage heart failure does not stem from myosin isozyme redistribution. This study found no significant changes in myosin isoenzyme patterns in diseased hearts, suggesting other mechanisms are at play.

Area of Science:

  • Cardiology
  • Biochemistry
  • Molecular Biology

Background:

  • End-stage heart failure is characterized by reduced cardiac function.
  • Myofibrillar ATPase activity is crucial for heart muscle contraction.
  • Altered myosin isozyme distribution has been proposed as a cause for reduced ATPase activity.

Purpose of the Study:

  • To investigate if reduced myofibrillar ATPase activities in end-stage heart failure are linked to myosin isozyme redistribution.
  • To compare ATPase activities and myosin isozyme patterns in normal and failing human hearts.

Main Methods:

  • Isolation of cardiac myofibrils from human hearts (normal and end-stage failure).
  • Measurement of myofibrillar Ca2(+)-dependent Mg-ATPase and myosin Ca2(+)- and K+EDTA-ATPase activities.
  • Analysis of myosin isozyme distribution using polyacrylamide gel electrophoresis.

Main Results:

  • Significant reduction in myofibrillar Ca2(+)-dependent Mg-ATPase observed in all studied heart failure models.
  • No changes in myofibril sensitivity to Ca2+ were noted.
  • Myosin Ca2(+)-ATPase was lower only in coronary artery disease hearts; K-EDTA ATPase showed no differences.
  • Polyacrylamide gel electrophoresis revealed no apparent differences in myosin isoenzyme patterns between normal and diseased hearts.

Conclusions:

  • Reduced myofibrillar ATPase activity in end-stage heart failure is not associated with myosin isozyme redistribution.
  • The mechanisms underlying decreased ATPase activity in heart failure require further investigation.
  • Further research is needed to clarify the ATPase nature of observed myosin bands.

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