An Observation of Thromboxane A₂ in Arterial Blood after Cholesterol Feeding in Rabbits

Abstract

Agents responsible for the entry of cholesterol-bearing lipoproteins into the arterial wall represent local risk factors in atherogenesis. In an attempt to identify these agents, we inserted a catheter into the ascending aorta of rabbits and 5ml of arterial blood sample was withdrawn. The contraction of the aortic strip of rabbit against Piper and Vane's antagonists with application of this sample was observed. Samples ob-tained after feeding of 1Gm/Kg of cholesterol and after an intravenous administration of thromboxan A₂ (TXA₂) contracted the aortic strip. Samples from non-treated rabbits or those obtained after intravenous administration of 10μg of epinephrine or norepinephrine did not contract the strip. Previous administration of 20mg/Kg of indomethacin decreased the contraction developed after feeding of 1Gm/Kg of cholesterol. It was suggested that TXA₂ might be released into the arterial blood by the ingestion of cholesterol and might be one of the agents responsible for the entry of lipoproteins.