Effects of chronic growth hormone hypersecretion on intrinsic contractility, energetics, isomyosin pattern, and myosin adenosine triphosphatase activity of rat left ventricle.
Why the study?
Does chronic growth hormone hypersecretion alter intrinsic contractility and energetics in the rat left ventricle?
Population
Rats bearing a growth hormone (GH)-secreting tumor
Comparison
Induction of a growth hormone (GH)-secreting tumor vs Control rats
Design
Preclinical
Follow-up
18 weeks
Authors
Discussion
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Implication
Enhances rat LV performance and economy under GH excess; leaves open translation to human acromegaly or HF.
Key Points
- To determine how chronic growth hormone hypersecretion affects left ventricular mechanics, contractile energetics, myosin isoform composition, and ATPase activity.
- Studied left ventricles and isolated papillary muscles from rats 18 weeks following growth hormone-secreting tumor induction alongside controls.
- Measured isometric force, unloaded shortening velocity, force-velocity relations, isomyosin distribution, and calcium- and actin-activated myosin ATPase activity.
- Maximum isometric force per cross-sectional area increased by +42% (P < 0.05 vs. controls) with unchanged unloaded shortening velocity and a +64% increase in force-velocity curvature (P < 0.05 vs. controls).
- Left ventricular isomyosin exhibited a significant shift toward the V3 isoform (32 ± 5% vs. 8 ± 2% in controls, P < 0.001), with alkaline sensitivity confirming V3 active enzymatic site involvement.
Structured PICO
Does chronic growth hormone hypersecretion alter intrinsic contractility and energetics in the rat left ventricle?
P
Population
Rats bearing a growth hormone (GH)-secreting tumor
I
Intervention
Induction of a growth hormone (GH)-secreting tumor
C
Comparator
Control rats
O
Outcome
Papillary muscle mechanics, energetics, myosin phenotype, and ATPase activities in left ventriclessurrogate
Chronic growth hormone hypersecretion in rats leads to myocardial adaptation that simultaneously improves contractile performance and economy.
Cite This Study
Timsit et al. (1990) studied this question.