Antiradical function of sulfhydryl residues and oxidative stress markers in dairy cattle plasma

The antiradical function of sulfhydryl (SH) residue in dairy cattle plasma and the relationship of SH residue concentrations to other oxidative stress markers, ascorbic acid and thiobarbituric acid reactive substance (TBARS) in plasma were investigated. The concentration of reduced glutathione (GSH) in phosphate buffer solution (pH 7.6) and SH residues in dairy cattle plasma decreased significantly (P < 0.05) in vitro by the addition of peroxyradicals at 38°C, depending on incubation periods. The decrease of GSH concentration with the peroxyradical solution was partially protected by the addition of sodium ascorbate solution. A positive and significant correlation with SH residues and albumin concentration in the fresh plasma obtained from 15 dairy cattle was observed (P < 0.05). The SH residue concentration was not correlated with the TBARS concentration in plasma. The total ascorbic acid and SH residues concentration in the plasma correlated positively but not significantly (P < 0.10). These results suggested that SH residues in dairy cattle plasma play important part in the antiradical function.