Gender differences in coronary artery diameter reflect changes in both endothelial Ca2+ and ecNOS activity

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.