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Pyridoxalated hemoglobin polyoxyethylene conjugate (PHP) on the endothelium-dependent relaxation in rat mesenteric
H Matsumura1, H Araki, T Morioka
1Department of Pharmacology and Anesthesiology, Kumamoto University Medical School, Japan.
Abstract:
Effects of exchange-transfusion with a modified hemoglobin (pyridoxalated hemoglobin polyoxyethylene conjugate; PHP) on diameter of rat mesenteric arterioles responding to various vasoactive substances were examined using the image-splitter television microscopy method. The mesentery of the anesthetized rat was spread over the stage of a microscope and the microvasculature was visualized by transillumination. Exchange-transfusion with a 6%PHP solution (30 ml/kg) was performed and effects of topical application of norepinephrine (NE) and acetylcholine(ACh) on diameter of mesenteric arterioles were examined. By exchange-transfusion with PHP, NE induced a dose-dependent decrease in diameter, while ACh induced a dose-dependent increase in diameter of the arterioles preconstricted by NE. There was no difference in vascular responsiveness to ACh and NE before and after exchange-transfusion with PHP solution. Results suggest that circulating PHP moiety does not exert any action on function of endothelial cell to release endothelium-derived relaxing factor (EDRF) in rat mesenteric microvasculature in situ.