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Myofibrillar ATPase, DNA and hydroxyproline content of human hypertrophied heart
Insights
This study found a negative correlation between heart DNA content and myofibrillar ATPase activity in human hearts. This suggests reduced ATPase activity in heart hypertrophy may stem from increased cellular polyploidy.
Area of Science:
- Cardiology
- Biochemistry
- Molecular Biology
Background:
- Human heart hypertrophy is associated with cellular changes.
- Understanding the biochemical alterations in hypertrophied hearts is crucial for disease management.
Purpose of the Study:
- To investigate the relationship between DNA content, collagen, and myofibrillar ATPase activity in human hearts.
- To explore the implications of these findings in the context of human heart hypertrophy.
Main Methods:
- Analysis of DNA, hydroxyproline (collagen marker), and myofibrillar Ca2+ and Mg2+ ATPase activity.
- Homogenization of myocardial tissue from 70 human hearts studied post-mortem.
- Comparison of post-mortem tissue with fresh biopsies from open-chest surgery.
Main Results:
- Normal hearts showed consistent DNA, collagen, and ATPase levels compared to fresh biopsies.
- Heart weight correlated positively with DNA content and negatively with myofibrillar ATPase.
- A significant negative correlation was observed between heart DNA content and Mg2+/Ca2+ myofibrillar ATPase activity.
Conclusions:
- Decreased myofibrillar ATPase activity in human heart hypertrophy may be linked to increased cellular polyploidy.
- The findings provide insights into the molecular mechanisms underlying cardiac remodeling in hypertrophy.
Abstract:
70 human hearts were studied less than 36 hours after death. The apex, and in some cases other parts of the myocardium were homogenized, DNA, hydroxyproline content, myofibrillar Ca2+ and Mg2+ ATPase were measured. In normal hearts the DNA and collagen content were 372 +/- 9 mg and 36 +/- 7 mg. Ca2+ and Mg2+ ATPase of the myofibrils prepared from these hearts have shown the same specific activity (35 +/- 5 and 34 +/- 6 nmol/min./mg) as those from fresh biopsies taken during open-chest surgery. The heart weight correlates with the DNA content (r= + 0.58 -p less than 0.01) and with the myofibrillar ATPase (r= - 0.33 - p less than 0.02) but not with the DNA concentration nor with the collagen content or concentration. The main result of this study was the presence of a negative correlation between the DNA content of the heart and the Mg2+ or Ca2+ myofibrillar ATPase (r= - 0.31, p less than 0.05 - r= - 0.45, p less than 0.01). This correlation was analysed with reference to the histological and biochemical studies published by several authors in human or experimental heart hypertrophy and it was suggested that in human heart hypertrophy the decrease of the myofibrillar or myosin ATPase is a direct consequence of the high degree of polyploidy of the muscular cells observed in this condition.