What question did this study set out to answer?

To determine whether alterations in myofibrillar contractile proteins contribute to increased myocardial force during chronic growth hormone hypersecretion.

January 1, 1993Circulation Research

Mechanical properties of rat cardiac skinned fibers are altered by chronic growth hormone hypersecretion.

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Why the study?

Does chronic growth hormone hypersecretion alter the mechanical properties of rat cardiac skinned fibers?

Population

Rats bearing a growth hormone (GH)-secreting tumor (GH rats)

Comparison

Chronic growth hormone (GH) hypersecretion vs Control rats

Design

Preclinical

Authors

EMEric MayouxBoehringer Ingelheim (Germany)RVRenée Ventura‐ClapierHeart Failure & Transplant JTJosé TimsitUniversité Paris Cité

Discussion

Member takes

Implication

GH hypersecretion may enhance rat myocardial mechanics; leaves open translation to human acromegaly cardiomyopathy.

Key Points

To determine whether alterations in myofibrillar contractile proteins contribute to increased myocardial force during chronic growth hormone hypersecretion.
Examined mechanical properties of chemically skinned cardiac fibers isolated from rats bearing growth hormone-secreting tumors and control rats to bypass excitation-contraction coupling.
Measured active tension and stiffness across calcium concentrations (pCa 4.5 and 9), crossbridge cycling rates through rapid length perturbations, and myosin heavy chain protein and mRNA expression.
At saturating calcium levels (pCa 4.5), maximal active tension was significantly higher in GH rats than in controls (52.9 ± 5.2 vs. 38.1 ± 4.6 mN·mm⁻², p < 0.05), as was stiffness (1,105 ± 120 vs. 685 ± 88 mN·mm⁻²·µm⁻¹, p < 0.01), with an increase in calcium sensitivity (ΔpCa 0.04, p < 0.001).
Crossbridge cycling rate was reduced in GH rats (62.0 ± 2.6 vs. 77.4 ± 6.6 s⁻¹, p < 0.05), which corresponded with a reduction in alpha-myosin heavy chains (45.5 ± 2.0% vs. 94.6 ± 2.4%, p < 0.001) and matching mRNA shifts.

Structured PICO

Does chronic growth hormone hypersecretion alter the mechanical properties of rat cardiac skinned fibers?

Population

Rats bearing a growth hormone (GH)-secreting tumor (GH rats)

Intervention

Chronic growth hormone (GH) hypersecretion

Comparator

Control rats

Outcome

Mechanical properties of cardiac skinned fibers (maximal active tension, stiffness, calcium sensitivity, crossbridge cycling rate)surrogate

Chronic growth hormone hypersecretion in rats increases myocardial contractility through alterations at the myofibrillar level, including increased maximal active tension and stiffness.

Cite This Study

Mayoux et al. (1993) studied this question.

synapsesocial.com/papers/6a7919cbc284d7a4ba5ae505 https://doi.org/10.1161/01.res.72.1.57

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Mechanical properties of rat cardiac skinned fibers are altered by chronic growth hormone hypersecretion.

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

Mechanical properties of rat cardiac skinned fibers are altered by chronic growth hormone hypersecretion.

Discussion

Member takes

Implication

Key Points

Structured PICO

Cite This Study

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