Cysteinyl-glycine in the control of glutathione homeostasis in bovine lenses.
OBJECTIVE
To define a possible metabolic and/or signaling role for Cys-Gly in glutathione homeostasis in bovine eye lenses.


METHODS
Bovine lenses were cultured up to 24 h in a medium containing 0.5 mM reduced glutathione (GSH) under different conditions. The intracellular and the extracellular contents of thiol compounds were evaluated using a free zone capillary electrophoresis method.


RESULTS
Culture of lenses in the presence of GSH and the gamma-glutamyl transferase inhibitor serine-borate demonstrated a 1.5 fold increase in the level of extra-lenticular glutathione with respect to the initial value. Cys-Gly exogenously added impaired the extra-lenticular accumulation of glutathione. Both cysteine and gamma-Glu-Cys were ineffective in reducing extra-lenticular glutathione accumulation. In all conditions no differences in reduced and total intra-lenticular glutathione levels were observed.


CONCLUSIONS
The impairment of Cys-Gly generation correlated with inhibition of gamma-glutamyl transferase by serine/borate, resulting in high extra-lenticular concentration of glutathione effluxed from the bovine lens. The possibility that Cys-Gly may intervene either in the replenishment processes for cysteine in the GSH biosynthetic step or in the function of the efflux GSH-transporters is considered.
De Donatis
Gian Marco
GM
Department of Biology, Biochemistry Unit, University of Pisa, Pisa, Italy.
Moschini
Roberta
R
Cappiello
Mario
M
Del Corso
Antonella
A
Mura
Umberto
U
D000818:Animals; D001881:Borates / Q000494:pharmacology; D002417:Cattle; D003545:Cysteine / Q000494:pharmacology; D004151:Dipeptides / Q000378:metabolism* / Q000494:pharmacology; D005978:Glutathione / Q000096:biosynthesis / Q000378:metabolism* / Q000494:pharmacology; D006706:Homeostasis / Q000502:physiology*; D007908:Lens, Crystalline / Q000201:enzymology / Q000378:metabolism*; D009994:Osmolar Concentration; D012694:Serine / Q000494:pharmacology; D046509:Tissue Culture Techniques; D014018:Tissue Distribution; D015854:Up-Regulation; D005723:gamma-Glutamyltransferase / Q000037:antagonists & inhibitors
D001881:Borates; D004151:Dipeptides; C040900:serine-borate complex; C028505:cysteinylglycine; D012694:Serine; D005723:gamma-Glutamyltransferase; D005978:Glutathione; D003545:Cysteine; C017341:gamma-glutamylcysteine