Oxygen radicals: effects on intestinal vascular permeability

Area of Science:

• Physiology
• Biochemistry
• Pathophysiology

Background:

• Oxygen-derived free radicals are implicated in vascular permeability changes during intestinal ischemia.
• Direct assessment of oxygen radical effects on intestinal vascular permeability is crucial.

Purpose of the Study:

• To directly evaluate the impact of oxygen free radicals on intestinal capillary permeability.
• To quantify the increase in vascular permeability induced by a specific oxygen radical-generating system.

Main Methods:

• Infusion of hypoxanthine-xanthine oxidase into feline ileal arteries to generate oxygen radicals.
• Estimation of osmotic reflection coefficient (sigma d) for plasma proteins using lymph-to-plasma protein ratio and lymph flow.
• Administration of free radical scavengers (superoxide dismutase, dimethylsulfoxide) to assess their protective effects.

Main Results:

• Hypoxanthine-xanthine oxidase infusion significantly reduced sigma d from 0.92 to 0.66, indicating increased intestinal vascular permeability.
• Superoxide dismutase (sigma d = 0.86) and dimethylsulfoxide (sigma d = 0.83) significantly attenuated the permeability increase.
• The observed increase in permeability was comparable to that seen after 1 hour of ischemia.

Conclusions:

• Oxygen-derived free radicals, generated by hypoxanthine-xanthine oxidase, markedly increase intestinal vascular permeability.
• Superoxide anion and hydroxyl radicals contribute to this oxygen radical-induced permeability increase.
• These findings highlight the role of oxygen radicals in the pathophysiology of intestinal ischemia.