DIFFERENTIAL CYTOPROTECTION BY GLYCINE AGAINST OXIDANT DAMAGE TO PROXIMAL TUBULE CELLS

Tert-butyl hydroperoxide (tBHP) injured freshly isolated proximal tubu les in an Fe-dependent fashion that was ameliorated by a lipophilic an tioxidant. diphenyl-p-phenylenediamine (DPPD), but was only minimally affected by glycine. Menadione-induced injury was Fe-independent and w as unaffected by DPPD, but was strongly blocked by glycine. Fe was hig hly toxic when intracellular loading was facilitated by concomitant tr eatment with hydroxyquinoline (HQ). This toxicity was blocked by DPPD or chelating the Fe, but not by glycine. All of the lesions were chara cterized by severe depletion of glutathione and other soluble thiols. Menadione induced large increases in protein associated with the Trito n-insoluble cytoskeleton and decreases in protein thiol content, consi stent with extensive cross linking, but did not increase thiobarbituri c acid reactive substances (TEARS). tBHP and HQ+Fe had either no effec t or only moderate, delayed effects on cytoskeletal proteins, but indu ced substantial increases of TEARS. Glycine did not the alter changes in cytoskeletal proteins, thiols, or TEARS produced by any of the agen ts. Protection against tBHP toxicity by deferoxamine and DPPD was acco mpanied by substantial suppression of TEARS accumulation. Superimposit ion of hypoxia during tBHP exposure reduced TEARS accumulation and res tored cytoprotective activity to glycine Thus, in contrast to its cons istently strong cytoprotection against a number of other insults, glyc ine is only variably cytoprotective against oxidant lesions in freshly isolated proximal tubules. Extensive oxidative crosslinking of protei ns is compatible with maintenance of glycine cytoprotection against le thal membrane damage. Fe-induced injury to proximal tubules associated with lipid peroxidation as manifested by TEARS formation is a relativ ely glycine-insensitive insult.