Release of Contracting Autacoids by Aortae of Normal and Atherosclerotic Rabbits

Summary: The aim of our study was to examine the release of various lipid and peptide contracting autacoids by aortae of normal and atherosclerotic rabbits. Leuko-triene (LT) E4, an enzymatic derivative of LTC4, thromboxane (Tx) B2, and endothelin-1 (ET-1) were measured by radioimmunoassay techniques in aortic preparations of normal and cholesterol-fed rabbits. Intact aortae of normal rabbits incubated with the calcium ionophore A23187 for 1 h at 37[degrees]C released LTE4 and TxB2 (22 +/- 3.5 and 14.8 +/- 2 pg/mg of tissue, respectively, mean +/- SEM, n = 33). Removal of aortic endothelium was associated with a significant reduction in LTE4 (44%) and TxB2 (58%) release. In aortic preparations from cholesterol-fed rabbits, the release of LTE4 was significantly enhanced (41 +/- 8 pg/mg of tissue, mean +/- SEM, n = 27) whereas TxB2 was not significantly altered. No detectable amounts of ET-1 were measured after 1 h of incubation. However, at 4 h, an endothelium-dependent release of ET-1 from normal aortae was demonstrated. In atherosclerotic aortae, ET-1 release was significantly higher than in controls (10 +/- 1.3 vs. 5 +/- 0.5 pg/cm2, mean +/- SEM, n = 16). We conclude that enhanced formation of vasoconstrictor autacoids may contribute to altered va-somotion of atherosclerotic blood vessels..