Determination of prostaglandin profiles in lipopolysaccharide-challenged guinea pig spleen.

We previously reported that splenic extract from lipopolysaccharide (LPS)-challenged guinea pigs inhibits the exaggerated febrile response of splenectomized guinea pigs, suggesting that the spleen generates an inhibitory factor. Earlier results indicate that the factor is a lipid. In an effort to identify this factor, lipid fractions, isolated from splenic extracts of control and LPS-challenged guinea pigs, were analyzed with emphasis on identifying and quantifying prostanoids, which according to current knowledge are the likely bioactive factors. Prostaglandins have been extensively implicated in central and peripheral thermoregulation, and thus these lipids were targeted for characterization in the spleen. Analysis was done on the splenic extracts using solid-phase extraction, analytical and preparative thin-layer chromatography (TLC) and high-performance liquid chromatography-mass spectrometry (HPLC-MS/MS). Four prostaglandins (PGs, 6-keto-PGF(1α) , PGF(2α) , PGE(2) and PGD(2) ) were identified and quantified. Our data shows that these PG levels are doubled in LPS-treated guinea pig spleen compared with the control group. The methods used in this investigation to characterize PG in the spleen offer significant advantages over immunoassays previously used to identify and quantify PG in the spleen and other biological tissues. These methods will be utilized in further research needed to definitively characterize the role of splenic-derived PG in modulation of the febrile response induced by LPS.