Nitroglycerin tolerance: different mechanisms in vascular segments with or without intact endothelial function

Area of Science:

• Cardiovascular Pharmacology
• Endothelial Function Research
• Drug Tolerance Mechanisms

Background:

• In vivo tolerance to nitroglycerin is linked to increased vascular superoxide anion levels.
• Endothelial function influences nitroglycerin tolerance; its removal can reverse tolerance in normal vessels.
• The effect of in vivo endothelial dysfunction on nitroglycerin tolerance remains unexamined.

Purpose of the Study:

• To investigate how in vivo endothelium denudation impacts the development of in vivo nitroglycerin tolerance.
• To assess the influence of endothelial integrity on the efficacy of interventions aimed at inhibiting nitroglycerin tolerance.

Main Methods:

• Conscious rat model with prolonged continuous nitroglycerin infusion.
• In vivo and ex vivo (myograph experiments) assessment of vascular reactivity to nitroglycerin.
• Comparison of endothelium-denuded versus endothelium-intact arteries.

Main Results:

• In vivo endothelium denudation did not alter the degree of nitroglycerin tolerance development.
• Superoxide dismutase and losartan significantly inhibited tolerance in endothelium-intact vessels but not in denuded segments.
• Interventions showed reduced efficacy in preventing tolerance in endothelium-denuded arteries compared to intact ones.

Conclusions:

• The presence or absence of in vivo dysfunctional endothelium significantly alters the effectiveness of interventions targeting nitroglycerin tolerance.
• Endothelial integrity is crucial for the success of pharmacological strategies aimed at mitigating nitroglycerin tolerance.