CYCLOSPORINE AND OXIDIZED LIPOPROTEINS AFFECT VASCULAR REACTIVITY - INFLUENCE OF THE ENDOTHELIUM

Cyclosporine and in particular oxidatively modified low density lipoproteins can both exert direct vasoconstricting effects. We hypothesized that coincubation of arteries with low density lipoproteins and cyclosporine would enhance their respective influence on vascular tone. Therefore, we investigated vascular reactivity of isolated intact rabbit renal arteries preincubated with cyclosporine in the presence of native and oxidized low density lipoproteins. After preincubation of the arteries with cyclosporine (10 mug/ml, 90 minutes), unstimulated vascular tone as well as norepinephrine-induced vasoconstrictions remained unchanged compared with controls preincubated with the cyclosporine solvent dimethyl sulfoxide. Oxidized low density lipoproteins (100 mug/ml) in the absence of cyclosporine significantly enhanced vasoconstrictions to threshold concentrations of norepinephrine (78+/-10 mum at 30 nM). However, after cyclosporine treatment, the oxidized low density lipoprotein-induced potentiation of contractile responses to norepinephrine was further enhanced (157+/-19 versus 71+/-11 mum). Native low density lipoproteins had no influence on vascular tone. Potentiation of norepinephrine-induced vasoconstriction by oxidized low density lipoproteins took place in either endothelium-denuded or endothelium-intact arteries, whereas the further enhancement of vascular tone after cyclosporine treatment was seen only in endothelium-intact segments. Endothelium-dependent dilations to acetylcholine were fully preserved after treatment with oxidized low density lipoproteins and cyclosporine. Indomethacin, saralasin, and the thromboxane A2 antagonist daltroban had no influence, but the Ca2+ antagonist verapamil prevented the potentiation of vasoconstrictions by cyclosporine and oxidized low density lipoproteins. These data indicate that coincubation of isolated renal arteries with cyclosporine and oxidized low density lipoproteins potentiates norepinephrine-induced vasoconstriction by a Ca2+- and partially endothelium-dependent mechanism before the onset of severe damage of the vasculature.