The relationship between nitric oxide synthase expression and nitric oxide mediated inhibition of vasoconstriction

• Author / Creator

  Liu,Sixue

• Nitric oxide (NO) is a ubiquitous signal molecule with many biological functions. NO is produced through the reaction of L-arginine with O2, which is catalyzed by the family NO synthase (NOS) enzymes. NOS exists in endothelial (eNOS), neuronal (nNOS) and inducible (iNOS) isoforms and the eNOS and nNOS isoforms are constitutively expressed in many tissues, including skeletal muscle and the endothelium. In the cardiovascular system, NO acts as a vasodilator and an inhibitor of sympathetic vasoconstriction and is important in the regulation of vascular resistance and blood flow response to exercise. Indeed, reduced NOS expression has been linked to vascular dysfunction and the pathogenesis of cardiovascular diseases such as essential hypertension. The relationship between NOS expression and cardiovascular disease suggests that NOS expression is an important determinant of NO bioavailability. Thus, the purpose of this thesis was to investigate the effect of sex, estrogen and exercise training on skeletal muscle NOS expression, as well as the relationship between NOS expression and NO mediated inhibition of sympathetic vasoconstriction. Sprague-Dawley rats (~10 weeks of age; n=49) were utilized. The percentage change of femoral vascular conductance (FVC) in response to sympathetic chain stimulation delivered at 2 and 5 Hz determined at rest and during triceps surae muscle contraction before and after non-selective NOS blockade L-NAME and skeletal NOS expression were measured. nNOS expression was greater in female compared to male rats. However, the greater nNOS expression in females does not appear to be a function of estrogen status as NOS expression was not different between ovary-intact, ovariectomized and ovariectomized-estrogen supplemented female rats. Furthermore, in contrast to our previous findings in male rats, exercise training does not appear to augment NOS expression in female rats skeletal muscle NOS expression was not correlated to the NO-mediated the inhibition of sympathetic vasoconstriction resting and contracting skeletal muscle. These results suggest that other factors beyond NOS expression modulate NO bioavailability and determine the magnitude of NO dependent sympatholysis. Further study will be required to fully elucidate the mechanism behind the enhanced sympatholysis in females.

• Subjects / Keywords

  • Nitric oxide
  • Nitric oxide synthase expression
  • Relationships

• Graduation date

  Spring 2018

• Type of Item

  Thesis

• Degree

  Master of Science

• DOI

  https://doi.org/10.7939/R3PC2TQ7B

• License

  This thesis is made available by the University of Alberta Libraries with permission of the copyright owner solely for non-commercial purposes. This thesis, or any portion thereof, may not otherwise be copied or reproduced without the written consent of the copyright owner, except to the extent permitted by Canadian copyright law.