Differential distribution of glutathione and glutathione-related enzymes in rabbit kidney. Possible implications in analgesic nephropathy

Abstract

Whole tissue reduced glutathione (GSH) concentration was found to be lowest in rabbit renal inner medulla and progressively higher in outer medulla and cortex. Activities of cytosolic glutathione reductase in inner medulla and outer medulla were similar, and each was only approximately 50% of that of cortex. Whole tissue and microsomal gamma-glutamyl transpeptidase activities were high in cortex and outer medulla but were low in inner medulla. Cytosolic activity of selenium-dependent glutathione peroxidase ( GPx -I) was similar in both outer medulla and inner medulla but was only 50% of that of cortex. Activity of cytosolic selenium-independent glutathione peroxidase ( GPx -II) was highest in cortex and lowest in inner medulla (approximately 15% of cortex and approximately 50% of outer medulla). Cytosolic glutathione S-transferase activity with 1-chloro-2,4-dinitrobenzene as substrate was high in all three regions of kidney. With 1,2-dichloro-4-nitrobenzene and 1,2-epoxy-(4-nitrophenoxy)propane as substrates, cytosolic glutathione S-transferase activities were very low in cortex, outer medulla, and inner medulla. Microsomal activities of glutathione reductase, GPx -I, GPx -II and glutathione S-transferases were much lower than activities of corresponding cytosolic enzymes. Activities of the glutathione peroxidases in renal inner medulla would hence be expected to cause little interference to prostaglandin endoperoxide synthetase mediated cooxidative activation of paracetamol. It has been demonstrated that the paracetamol metabolite can react rapidly with GSH, forming not only glutathione conjugate but also paracetamol itself and oxidized glutathione. Low GSH concentrations, as well as low activities of glutathione reductase, GPx -I, GPx -II, and gamma-glutamyl transpeptidase, may therefore render the inner medullary region of kidney particularly vulnerable to paracetamol-related analgesic nephropathy.