Time-course of changes in plasma nitric oxide following lipopolysaccharide and turpentine injection in rats

The effect of lipopolysaccharide (LPS) and turpentine on nitric oxide (NO) production were investigated in rats. Because of short half-life of NO in biological fluids, the plasma nitrite and nitrate concentrations (two stabile metabolites of NO) were measured based on Griess reaction, which is indirect assay for NO production. Injection of LPS at an intraperitoneal dose of 50 μg/kg caused a 3,5-fold increase in plasma nitrite within 3 h and nitrite levels remained significantly elevated 6, 12, and 24 h after endotoxin treatment with LPS. However, injection of turpentine at an intramuscular dose of 20 μl/rat did not alter plasma nitrite concentration at selected times after turpentine treatment (7, 10, 14, and 24 h postinjection). These results further support the hypothesis that NO is involved in pathogenesis of febrile response due to LPS in rats. Because turpentine did not change concentration of NO in plasma, the role of NO, as mediator/modulator, in development of turpentine fever appears to be controversial and needs further experimental verification.