Effects of adrenaline or endotoxin tolerance states on mesenteric blood flow in endotoxaemia

Background: Endotoxic shock is associated with release of catecholamines as well as decreased mesenteric vascular perfusion, which is thought to cause remote organ injury, Adrenaline tolerance; was reported to decrease mortality in endotoxic shock and have cross-tolerance with endotoxin tolerance, Our aim was to investigate the effect of these two tolerance conditions on the lipopolysaccharide (LPS)-induced decrease in mesenteric blood flow (MBF), Methods: Adrenaline tolerance was developed by injecting 0.03 mg/kg adrenaline to Swiss-albino mice, gradually increasing the dose to 2 mg/kg over 5 days. Endotoxin tolerance was developed by injecting saline for 4 days and LPS 1 mg/kg at the fifth day. Control animals were injected with saline for 5 days, At 72 h after completion of injections, half of the animals in each group were challenged with saline and the other half with 20 mg/kg LPS, at 0 h. Mesenteric blood flow was measured at 4 and 24 h. Results: Neither endotoxin nor adrenaline tolerance prevented an LPS-induced decrease in MBF. Conclusion: A low dose of LPS prior to a higher dose does riot prevent an LPS-induced decrease in MBF and may actually prime for a decrease. Also, catecholamines are not primary mediators of LPS-induced decreases in MBF.