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Xanthine oxidase and endothelium dependent relaxation
Biochemical and Biophysical Research Communications
|September 15, 1987
Summary
Xanthine oxidase can cause endothelium-dependent relaxation, independent of its oxidative properties. This relaxation is likely due to trypsin contamination, not superoxide anion effects on endothelium-derived relaxing factor.
Area of Science:
- Biochemistry
- Physiology
- Enzymology
Background:
- Superoxide anion (O2-) from xanthine oxidase/xanthine can reduce endothelium-derived relaxing factor (EDRF) half-life.
- Xanthine oxidase itself induces endothelium-dependent relaxation, separate from its oxidative function.
Purpose of the Study:
- To investigate the mechanism behind xanthine oxidase-induced endothelium-dependent relaxation.
- To determine if this relaxation is related to the enzyme's oxidative properties or other factors.
Main Methods:
- Studied endothelium-dependent relaxation induced by xanthine oxidase.
- Tested the effects of allopurinol (xanthine oxidase inhibitor), indomethacin (cyclooxygenase inhibitor), and p-bromophenacyl bromide (phospholipase A2 inhibitor).
- Investigated the role of trypsin inhibitor (TI) and compared relaxation effects of trypsin, chymotrypsin, and carboxypeptidase.
Main Results:
- Xanthine oxidase-induced relaxation was not inhibited by allopurinol, indomethacin, or p-bromophenacyl bromide.
- The relaxation was inhibited by trypsin inhibitor (TI).
- Trypsin and pancreatin (containing trypsin) also elicited similar TI-inhibited relaxation, while chymotrypsin and carboxypeptidase had minimal effect.
Conclusions:
- Endothelium-dependent relaxation by xanthine oxidase is likely caused by trypsin contamination, not its superoxide-generating activity.
- Using purified xanthine oxidase is crucial when studying oxygen radicals' effects on EDRF to avoid confounding factors.