Studies into sulfur amino acid and bile salt metabolism in pancreatic and liver diseases. Profiles of sulfur amino acids and glutathione in acute pancreatitis; method development for total and oxidized glutathione by liquid chromatography; bile salt profiles in liver disease by liquid chromatography-mass spectrometry.

摘要

Sulfur amino acids have critical function as intracellular redox buffers and maintainudhomeostasis in the external milieu by combating oxidative stress. Synthesis ofudglutathione (GSH) is regulated at a substrate level by cysteine, which is synthesized byudhomocysteine via the transsulfuration pathway. Oxidative stress and diminishedudglutathione pools play a sustained role in the pathogenesis of acute pancreatitis.udOne of the aims of this study was to experimentally address the temporal relationshipudbetween plasma sulfur amino acid levels in patients suffering from acute pancreatitis.udThe data indicated low concentration of cysteine initially, at levels similar to those ofudhealthy controls. Glutathione was found reduced whilst cysteinyl-glycine and ¿-udglutamyl transpeptidase activity were increased in both mild and severe attacks. As theuddisease progressed, glutathione and cysteinyl-glycine were further increased in mildudattacks and cysteine levels correlated with homocysteine and ¿-glutamyl transpeptidaseudactivity. The progress of severe attacks was associated with glutathione depletion,udreduced ¿-glutamyl transpeptidase activity and increased cysteinyl-glycine, thatudcorrelated with glutathione depletion. The corollary that ample supply of cysteine andudcysteinly-glycine does not contribute towards glutathione synthesis in acute pancreatitisudposes an important issue that merits resolution. Heightened oxidative stress anduddepletion of glutathione rationalized the progression of disease in severe attacks.udAn upsurge that reactive oxygen species can shift redox state of cells is determined byudthe ratio of the abundant redox couples reduced and oxidized glutathione (GSH: GSSG)udin cell. The study reported a novel methodology for quantification of total oxidizedudglutathione (tGSSG) and total glutathione (tGSH) in whole blood using reverse phaseudhigh performance liquid chromatography. The novelty of the method is ascertained byudthe use of a mercaptan scavenger 1, methyl-2-vinyl-pyridinium trifluromethanesulfonateudfor the total oxidized glutathione determination. The results reported permit quantitationudof tGSSG and tGSH and was applied to a control group.udFinally, the study was also focussed in developing a liquid chromatography-massudspectrometric method to evaluate free and conjugated bile acids in patients sufferingudfrom various degrees of cholestatic-hepatobiliary disorders. The study reported lowudlevels of ursodeoxycholic acid (UDCA) and slightly high levels of lithocholic acidud(LCA). All the primary bile acids seem to be conjugated with glycine and taurine aminoudacid.