Ergothioneine distribution in bovine and porcine ocular tissues

Ergothioneine (ERT), is a low molecular weight, sulfur-containing antioxidant occurring in up to millimolar amounts in mammalian tissues. Using an improved HPLC assay, ERT levels have been measured and compared in bovine and porcine eyes and erythrocytes. The rank order of ERT levels in bovine ocular tissue was lens > retina = cornea > pigmented retinal epithelium (RPE) > aqueous humor (AQ) > vitreous humor (VIT) > sclera. In porcine ocular tissue, the rank order was retina > AQ > VIT > RPE > cornea > lens > sclera. ERT levels in bovine lens were about 250 x > that in porcine lens. Porcine erythrocyte levels were 5.5 x > bovine levels. Species differences were also observed in the retina, VIT and AQ where porcine levels were 2 to 10-fold greater than bovine levels. ERT in bovine lens and cornea was 35 and 14 times greater than the corresponding level of reduced glutathione (GSH). Porcine lens had 45 times more GSH than ERT. Values for ERT and GSH in other tissues from both species were of the same order of magnitude. These results are consistent with a role for ERT in prevention of oxidative damage to the eye.