Glutathione-dependent detoxification of peroxide in bovine ciliary body

Abstract

Perfusion of the bovine eye with a buffer solution containing t-butyl hydroperoxide and the glutathione reductase inhibitor nitrofurantoin caused significant decreases in reduced glutathione level in ciliary body and iris. The result was interpreted to suggest that the organic hydroperoxide was decomposed by the glutathione peroxidase-reductase system. The glutathione reductase reaction requires NADPH. Since the level of NADPH is maintained by the hexose monophosphate shunt in many tissues, we investigated whether this is also the case with bovine uveal tissues. CO 2 formation from [1- 14C]glucose but not from [6- 14C]glucose was markedly stimulated by t-butyl hydroperoxide and was inhibited by the glutathione reductase inhibitor 1,3-bis(2-chloroethyl)-1-nitrosourea, thus supporting the importance of the hexose monophosphate shunt for hydroperoxide decomposition through the glutathione peroxidase-reductase system. The peroxidase-reductase activity was found both in non-pigmented and pigmented ciliary epithelial cells in culture. Purification studies isolated two forms of glutathione reductase [GR I (140 kDa) with subunit Mr of 70 kDa and GR II (> 670 kDa) with subunit Mr of 45 kDa] and a novel glutathione peroxidase (112 kDa with subunit Mr of 29 kDa). The peroxidase is active both with H 2O 2 and organic hydroperoxides, does not contain selenium and shows no glutathione S-transferase activity.