Inflammation induced by either endotoxin or vaccination has previously been shown to impair endothelium-dependent vasodilation (EDV) in healthy young individuals. However, the vascular effects of these two mechanisms of inducing inflammation have not been compared in the same individuals. Twelve young healthy males were studied at the same time of the day on three occasions in a random order; on one occasion 4 hours following an endotoxin injection (Escherichia coli endotoxin, 20 IU/kg), on another occasion 8 hours following vaccination against Salmonella typhi, and on a third occasion 4 hours following a saline control injection. EDV and endothelium-independent vasodilation (EIDV) were evaluated by local infusions of acetylcholine and sodium nitroprusside in the brachial artery, and forearm blood flow was measured with venous occlusion plethysmography. The augmentation index was determined by pulse wave analysis as an index of pulse wave reflection. Both endotoxin and vaccination impaired EDV to a similar degree compared with the saline control (P = 0.005 and P = 0.014, respectively). EIDV was not significantly affected by inflammation. Endotoxin, but not vaccination, increased body temperature and circulating levels of intracellular adhesion molecule-1 and interleukin-6. Augmentation index was not affected by the interventions. Despite the fact that endotoxin induced a more pronounced degree of inflammation than vaccination, both inflammatory challenges impaired EDV to a similar degree, supporting the view that different inflammatory stimuli could induce harmful effects on the vasculature.
