Arteriolar endothelium-dependent vasodilation occurs during endotoxin shock

Area of Science:

• Physiology
• Pharmacology
• Microcirculation

Background:

• Endotoxin shock is known to affect endothelial function in large arteries.
• In vitro studies suggest alterations in endothelial structure and function.
• The impact on microvascular arteriolar reactivity in vivo requires further investigation.

Purpose of the Study:

• To investigate the impact of endotoxin shock on cremaster muscle arteriolar dilator reactivity in rats.
• To assess the role of nitric oxide (NO) and its pathways in mediating these responses.
• To evaluate the potential of hydroquinone (HQ) in mitigating endotoxin-induced vascular dysfunction.

Main Methods:

• Pentobarbital-anesthetized rats received intravenous Escherichia coli endotoxin.
• Videomicroscopy was used to measure cremaster muscle arteriolar diameter.
• Acetylcholine (ACh) was administered intra-arterially to assess dilator responses.
• Methylene blue and hydroquinone (HQ) were used to probe the involvement of NO pathways.

Main Results:

• Endotoxin shock led to decreased arterial pressure and altered arteriolar diameter.
• Postendotoxin acetylcholine-induced dilation was attenuated, particularly in A1 arterioles.
• Methylene blue and HQ partially blocked ACh responses and affected NO release.
• HQ treatment partially restored ACh responses and significantly increased survival time.

Conclusions:

• Arteriolar endothelial cells remain functional and release nitric oxide (NO) during endotoxin shock.
• The microvascular NO release and ACh-induced dilation are attenuated by methylene blue and HQ.
• Hydroquinone may mitigate lethal effects associated with inducible NO synthase during endotoxin shock.