Age-related changes of plasma glutathione and cysteine in broilers: effect of dithiothreitol reduction vitro on free and bound pools

A study was conducted to determine free and protein-bound pools of glutathione and cysteine in the plasma of male broiler chicks. Birds were brooded in battery cages and provided ad libitum access to a starter diet and water. Plasma was treated with a reducing agent, dithiothreitol (DTT), or left untreated, and analyzed by HPLC to determine free and protein bound pools of reduced (GSH) and oxidized (GSSG) glutathione, cysteine (Cys), and cystine (Cyss). With respect to total plasma pools of GSH and Cys, between 0 and 21 d of age; 1) free GSH increased from 30 to 90% with a reciprocal decrease in protein-bound GSH, but GSSG was not detected; and 2) free Cys decreased from 20 to 10%, free Cyss increased from 24 to 45%, and protein-bound Cys decreased from 55 to 44%. The majority of the GSH plasma pool in this study was present in a free, acid-soluble form, whereas most of the total Cys pool was present as Cyss or bound to protein.