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Nitric oxide modulates the frog heart ventricle morphodynamics.

Raffaele Acierno1, Alfonsina Gattuso, Antonio Guerrieri

  • 1Department of Biological and Environmental Sciences and Technologies, University of Lecce, I-73100 Lecce, Italy.

Comparative Biochemistry and Physiology. Part A, Molecular & Integrative Physiology
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Nitric oxide (NO) in frog hearts reduces systolic function but improves diastolic filling. Inhibiting nitric oxide synthase (NOS) enhances contractility, yet impairs the heart's ability to fill.

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Area of Science:

  • Cardiovascular Physiology
  • Nitric Oxide Signaling
  • Amphibian Biology

Background:

  • The role of nitric oxide (NO) in cardiac function is complex and requires further elucidation, particularly in ectothermic vertebrates.
  • Understanding NO's influence on ventricular dynamics is crucial for comparative cardiovascular research.

Purpose of the Study:

  • To investigate the impact of nitric oxide (NO) on the ventricular systolic and diastolic functions of the avascular frog heart (Rana esculenta).
  • To explore the effects of modulating the nitric oxide synthase (NOS)-cyclic guanosine monophosphate (cGMP) pathway on cardiac mechanics.

Main Methods:

  • Utilized a novel video-based image analysis technique to monitor external ventricular volume variations throughout the cardiac cycle.
  • Quantified key hemodynamic parameters including end-diastolic volume (EDVext), end-systolic volume (ESVext), ejection fraction (EF), and contraction/relaxation velocities (dV/dtsys, dV/dtdia).
  • Administered various pharmacological agents, including NOS substrates, NO donors, NOS inhibitors, and guanylyl cyclase inhibitors, to assess their effects on cardiac function.

Main Results:

  • Nitric oxide (NO) was found to decrease ventricular systolic function while enhancing diastolic filling.
  • Inhibition of nitric oxide synthase (NOS) led to increased cardiac contractility but compromised ventricular filling capacity.
  • Morphological evidence of activated endothelial nitric oxide synthase (eNOS) supported the functional findings.

Conclusions:

  • The study demonstrates that nitric oxide (NO) plays a significant role in regulating frog ventricular function, balancing systolic and diastolic performance.
  • A tonic release of NO by NOS influences the mechanical activity of the frog ventricular pump.
  • Findings highlight the importance of the NOS-NOcGMP pathway in amphibian cardiac physiology.