Lipopolysaccharide dose response in baboons.

A lipopolysaccharide (LPS) dose-response study in an experimental baboon endotoxemia model is presented to define the relevance of this model compared with human endotoxemia. We describe acute and subacute endotoxemic models in baboons, the first evoked by bolus injection of LPS (1 mg, 0.1 mg, or 4 ng per kg of Escherichia coli LPS), and the second evoked by infusion of 1.5 mg/kg of E. coli LPS over 30 min. We report the analysis of LPS clearance, the kinetics of tumor necrosis factor, interleukin (IL) 6, and IL-8 expression on the protein as well as on the mRNA level, change in blood counts (white and red blood cells and circulating platelets), and several hemodynamic parameters such as temperature, cardiac index, heart rate, and mean arterial pressure via multiple sampling. The resulting data are compared with previously published human data. Our results show that the LPS-induced kinetics of cytokine release, as well as of hemodynamic and hematologic changes in baboons, were similar to those observed in humans, even though baboons required a approximately 104-fold higher initial LPS dose to develop these manifestations. Hence, we demonstrate that endotoxemia in baboons qualitatively, yet not quantitatively, resembles endotoxemia in humans and, therefore, proves to constitute a useful model for studying the pathogenic mechanisms of sepsis in relation to humans.

S-nitroso human serum albumin treatment reduces ischemia/reperfusion injury in skeletal muscle via nitric oxide release.

BACKGROUND: Peroxynitrite generated from nitric oxide (NO) and superoxide (O2-) contributes to ischemia/reperfusion (I/R) injury. Feedback inhibition of endothelial NO synthase by NO may inhibit O2- production generated also by endothelial NO synthase at diminished local L-arginine concentrations accompanying I/R. METHODS AND RESULTS: During hindlimb I/R (2.5 hours/2 hours), in vivo NO was monitored continuously (porphyrinic sensor), and high-energy phosphates, reduced and oxidized glutathione (chromatography), and I/R injury were measured intermittently. Rabbits receiving human serum albumin (HSA) (controls) were compared with those receiving S-nitroso human serum albumin (S-NO-HSA) beginning 30 minutes before reperfusion for 1 hour or 30 minutes before ischemia for 3.5 hours (0.1 micromol x kg(-1) x h(- 1)). The onset of ischemia led to a rapid increase of NO from its basal level (50+/-12 nmol/L) to 120+/-20 and 220+/-15 nmol/L in the control and S-NO-HSA-treated groups, respectively. In control animals, NO dropped below basal levels at the end of ischemia and to undetectable levels (<1 nmol/L) during reperfusion. In S-NO-HSA-treated animals, maximal NO levels never decreased below basal concentration and on reperfusion were 100+/-15 nmol/L (S-NO-HSA preischemia group, 175+/-15 nmol/L). NO supplementation by S-NO-HSA led to partial and in the preischemia group to total preservation of high-energy phosphates and glutathione status in reperfused muscle (eg, preischemia groups: ATP, 30.23+/-5.02 micromol/g versus control, 15.75+/-4.33 micromol/g, P<0.0005; % oxidized glutathione, 4.49+/- 1.87% versus control, 22.84+/-6.39%, P<0.0001). S-NO-HSA treatment in all groups led to protection from vasoconstriction and reduced edema formation after reperfusion (eg, preischemia groups: interfiber area, 12.94+/-1.36% versus control, 27.83+/-1.95%, P< 0.00001). CONCLUSIONS: Long-lasting release of NO by S-NO-HSA provides significant protection of skeletal muscle from I/R injury.