Abstract

The protective effects of polysaccharide peptide (PSP), isolated from Coriolus versicolor COV-1, on paracetamol-induced hepatotoxicity was investigated in this study. The effect of PSP on hepatic glutathione status was also studied. PSP (300 mg/kg, i.p.) caused a 40% depletion of hepatic reduced glutathione (GSH) with a concomitant 50% increase in oxidized glutathione (GSSG), thus producing a 3-fold increase in the GSSG/GSH ratio. The PSP-induced GSH depletion itself had no hepatotoxic effects. PSP protected against paracetamol-induced hepatotoxicity by decreasing the paracetamol-induced elevation of serum glutamic-pyruvic transaminase (SGPT) activity from 511 +/- 71 U/ml to 187 +/- 58 U/ml (controls without paracetamol 105 +/- 4 U/ml) and serum glutamic-oxaloacetic transaminase (SGOT) activity from 462 +/- 63 to 152 +/- 48 U/ml (controls without paracetamol 54 +/- 6 U/ml). PSP did not reverse the depletion of total glutathione (GSH+GSSG) by the toxic dose of paracetamol. The GSSG/GSH ratio, which is a measure of oxidative stress, was significantly (p < 0.05) decreased when PSP was coadministered with paracetamol. PSP dose-dependently decreased the covalent binding of [14C]-paracetamol to microsomal proteins in vitro. When PSP was given to rats subchronically for 7 days (300 mg/kg/day, i.p.), the subsequent microsomes obtained also showed a 25% decrease in covalent binding to [14C]-paracetamol, suggesting that PSP interacted with the microsomal proteins rather than the chemically reactive metabolite of paracetamol. The changes in the binding affinity and capacity of the microsomal proteins by PSP may be related to its ability to alter the redox potential as indicated by the effects of PSP on the GSSG/GSH status.