Chronic aerobic exercise associated to low-dose L-NAME improves contractility without changing calcium handling in rat cardiomyocytes

Braz J Med Biol Res. 2020 Mar 9;53(3):e8761. doi: 10.1590/1414-431X20198761. eCollection 2020.

Abstract

Nitric oxide (NO) inhibition by high-dose NG-nitro-L-arginine methyl ester (L-NAME) is associated with several detrimental effects on the cardiovascular system. However, low-dose L-NAME increases NO synthesis, which in turn induces physiological cardiovascular benefits, probably by activating a protective negative feedback mechanism. Aerobic exercise, likewise, improves several cardiovascular functions in healthy hearts, but its effects are not known when chronically associated with low-dose L-NAME. Thus, we tested whether the association between low-dose L-NAME administration and chronic aerobic exercise promotes beneficial effects to the cardiovascular system, evaluating the cardiac remodeling process. Male Wistar rats were randomly assigned to control (C), L-NAME (L), chronic aerobic exercise (Ex), and chronic aerobic exercise associated to L-NAME (ExL). Aerobic training was performed with progressive intensity for 12 weeks; L-NAME (1.5 mg·kg-1·day-1) was administered by orogastric gavage. Low-dose L-NAME alone did not change systolic blood pressure (SBP), but ExL significantly increased SBP at week 8 with normalization after 12 weeks. Furthermore, ExL promoted the elevation of left ventricle (LV) end-diastolic pressure without the presence of cardiac hypertrophy and fibrosis. Time to 50% shortening and relaxation were reduced in ExL, suggesting a cardiomyocyte contractile improvement. In addition, the time to 50% Ca2+ peak was increased without alterations in Ca2+ amplitude and time to 50% Ca2+ decay. In conclusion, the association of chronic aerobic exercise and low-dose L-NAME prevented cardiac pathological remodeling and induced cardiomyocyte contractile function improvement; however, it did not alter myocyte affinity and sensitivity to intracellular Ca2+ handling.

MeSH terms

  • Adiposity
  • Animals
  • Body Weight / physiology
  • Calcium / analysis*
  • Enzyme Inhibitors / administration & dosage
  • Enzyme Inhibitors / pharmacology*
  • Hemodynamics
  • Male
  • Models, Animal
  • Motor Activity / physiology
  • Myocardial Contraction / drug effects*
  • Myocardium / pathology
  • Myocytes, Cardiac / drug effects
  • Myocytes, Cardiac / physiology
  • NG-Nitroarginine Methyl Ester / administration & dosage
  • NG-Nitroarginine Methyl Ester / pharmacology*
  • Nitric Oxide Synthase / drug effects*
  • Nitric Oxide Synthase / metabolism
  • Physical Conditioning, Animal / physiology*
  • Rats, Wistar
  • Ventricular Pressure / drug effects

Substances

  • Enzyme Inhibitors
  • Nitric Oxide Synthase
  • Calcium
  • NG-Nitroarginine Methyl Ester