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Gender differences in coronary artery diameter reflect changes in both endothelial Ca2+ and ecNOS activity
H J Knot1, K M Lounsbury, J E Brayden
1Department of Pharmacology, University of Vermont College of Medicine, Burlington, Vermont 05405, USA.
The American Journal of Physiology
|March 10, 1999
Summary
Female rats exhibit greater nitric oxide (NO) production in coronary arteries due to higher endothelial cell calcium and enhanced endothelial constitutive nitric oxide synthase (ecNOS) activity, contributing to reduced myogenic tone.
Area of Science:
- Cardiovascular Physiology
- Endocrinology
- Biochemistry
Background:
- Gender differences influence coronary artery function, potentially mediated by nitric oxide (NO) release from the vascular endothelium.
- The precise mechanisms underlying gender-specific NO regulation in coronary arteries remain unclear.
Purpose of the Study:
- To investigate gender-associated differences in endothelial function and nitric oxide synthase (NOS) activity in rat coronary arteries.
- To elucidate the role of intracellular calcium ([Ca2+]i) and endothelial constitutive NOS (ecNOS) in these gender differences.
Main Methods:
- Measurement of coronary artery diameter, endothelial cell [Ca2+]i, and ecNOS enzymatic activity in pressurized arteries from female and male rats.
- Analysis of ecNOS activation kinetics and maximal activity in response to varying calcium concentrations.
Main Results:
- Coronary arteries from female rats constricted less than male rats under elevated pressure.
- Female arteries showed higher endothelial [Ca2+]i, which correlated with increased ecNOS activity.
- ecNOS activity and maximal activity were significantly higher in female coronary arteries compared to males.
Conclusions:
- Gender significantly impacts endothelial Ca2+ regulation and ecNOS activity in coronary arteries.
- These factors contribute to the observed lower myogenic tone in female coronary arteries, suggesting a nearly threefold greater tonic NO production in females.