Chronic endotoxemia and endothelium-dependent vasodilation in coronary arteries.

Endotoxin acutely decreases the production of nitric oxide, leading to abnormal regulation of coronary vascular tone: however, the effects of chronic endotoxemia on vasomotion are unknown. We therefore tested the hypothesis that chronic, low-level endotoxemia inhibits endothelium-dependent vasodilation. Rabbits were continuously infused with a subclinical dose of Escherichia coli endotoxin (.6 microgram/24 h, intraperitoneal) or saline for 5 wk. Endotoxin at this concentration elicited no significant sustained pyretic or hemodynamic responses. Both endothelium-dependent and independent vasomotor responses were determined in coronary arteries (250-500 mu). Vasorelaxation in response to acetylcholine, but no adenosine diphosphate (ADP), was significantly enhanced in endotoxin-challenged animals (EC50 = 62.6 +/- 11.1 nM, control vs. 33.97 +/- 5.7 nM, endotoxin-challenged; p < .05). Vasoconstriction to PGF2 alpha, but not KCl, was significantly decreased in endotoxin-challenged animals. These results indicate that endothelium-dependent and independent vasomotor responses are altered during chronic endotoxemia and are due, in part, to alterations in signal-transduction mechanisms specific for certain types of receptors.