Mildly oxidized low-density lipoprotein impairs responses of carotid but not basilar artery in rabbits.
OBJECTIVE
Intracranial blood vessels appear to be relatively resistant to development of atherosclerosis. The goal of this study was to compare effects of mildly oxidized LDL (ox-LDL) on endothelium-dependent responses of intracranial and extracranial arteries in vitro.


METHODS
LDL was purified from plasma of healthy subjects and mildly oxidized by means of a xanthine/xanthine oxidase reaction. Contraction of the rabbit basilar and carotid arteries in response to histamine and phenylephrine and relaxation in precontracted vessels to acetylcholine and sodium nitroprusside were evaluated after 30 minutes of exposure to LDL or ox-LDL (100 micrograms/mL).


RESULTS
Exposure to LDL had little or no effect on vascular responses. After exposure to ox-LDL, contraction to histamine and phenylephrine and relaxation to acetylcholine were impaired significantly in carotid (P < .05) but not in basilar artery. Relaxation to sodium nitroprusside was not significantly impaired by ox-LDL in the basilar artery. In the carotid artery, relaxation to sodium nitroprusside was significantly impaired by ox-LDL when the vessels were precontracted with phenylephrine but not histamine. Impairment of vascular responses by ox-LDL was prevented by addition of superoxide dismutase, catalase, or dimethylthiourea to the LDL solution before addition of xanthine/xanthine oxidase.


CONCLUSIONS
Mildly ox-LDL impairs contraction and endothelium-dependent relaxation in the carotid but not in basilar artery. Thus, intracranial arteries may be relatively resistant to mildly ox-LDL.
Napoli
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Department of Internal Medicine and Pharmacology, University of Iowa, Iowa City 52242-1081, USA.
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Faraci
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Taguchi
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D000818:Animals; D001488:Basilar Artery / Q000187:drug effects* / Q000502:physiology; D002339:Carotid Arteries / Q000187:drug effects* / Q000502:physiology; D004730:Endothelium, Vascular / Q000502:physiology; D006632:Histamine / Q000494:pharmacology; D006801:Humans; D008077:Lipoproteins, LDL / Q000494:pharmacology*; D008297:Male; D010656:Phenylephrine / Q000494:pharmacology; D011189:Potassium Chloride / Q000494:pharmacology; D011817:Rabbits; D014662:Vasoconstrictor Agents / Q000494:pharmacology; D014664:Vasodilation / Q000187:drug effects / Q000502:physiology
D008077:Lipoproteins, LDL; D014662:Vasoconstrictor Agents; C099252:oxidized low density lipoprotein; D010656:Phenylephrine; D011189:Potassium Chloride; D006632:Histamine