The Role of Endothelium in the Phenylephrine-Induced Oscillatory Responses of Rabbit Mesenteric Arteries

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Abstract
Phenylephrine-induced oscillatory contractions in rabbit mesenteric arteries were investigated in vitro. Adrenergic, cholinergic, or histamine antagonists as well as cyclooxygenase and lipoxygenase inhibitors had no effect on this phenylephrine-induced oscillation. The removal of extracellular calcium ions or treatment with a calcium antagonist reduced the amplitude and frequency of the oscillation. Removal of the endothelium or treatment with inhibitors of the synthesis or the target enzyme of endothelium-derived relaxing factor (EDRF) also reduced the amplitude and frequency of the oscillation. In a perfusion bioassay, the perfusate from an endothelium-intact arterial segment induced oscillation of an endothelium-denuded arterial ring recipient. These results suggest that phenylephrine-induced oscillation is mediated by an endothelium-derived factor such as EDRF and depends on the influx of extracellular calcium ions.