Release of contracting autacoids by aortae of normal and atherosclerotic rabbits

The aim of our study was to examine the release of various lipid and peptide contracting autacoids by aortae of normal and atherosclerotic rabbits. Leukotriene (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 vasomotion of atherosclerotic blood vessels.