s-(1-2-3-4-4-pentachloro-1-3-butadienyl)glutathione and Kidney-Diseases

Glutathione (GSH) conjugation reactions in the metabolism of hexachlorobutadiene (HCBD), in rats and mice, initiate a series of metabolic events resulting in the formation of reactive intermediates in the proximal tubular cells of the kidney. The GSH S-conjugate 1-(glutathion-S-yl)-1,2,3,4,4-pentachlorobutadiene (GPCB), which is formed by conjugation of HCBD with GSH in the liver, is not reactive and is eliminated from the liver in the bile or plasma, or both. GPCB may be translocated intact to the kidney and processed there by gamma-glutamyl transpeptidase and dipeptidases to the corresponding cysteine S-conjugate. Alternatively, gamma-glutamyl transpeptidase and dipeptidases present in epithelial cells of the bile duct and small intestine may catalyse the conversion of GPCB to cysteine S-conjugates. The kidney concentrates both GSH and cysteine S-conjugates and processes GSH conjugates to cysteine S-conjugates. A substantial fraction of HCBD cysteine S-conjugate thus concentrated in the kidney is metabolized by renal cysteine conjugate beta-lyase to reactive intermediates. The selective formation of reactive intermediates in the kidney most likely accounts for the organ-specific effects of HCBD. Alternatively, cysteine S-conjugates may be acetylated to yield excretable mercapturic acids.

Topics: Animals; Biotransformation; Butadienes; Cysteine; Glutathione; Kidney Diseases; Liver

Monolayers of LLC-PK1 cells, a cell line with features typical of proximal tubular epithelial cells, were treated at the apical and basolateral side with S-(1,2,3,4,4-pentachlorobutadienyl)glutathione (PCBD-GSH) and N-acetyl-S-(1,2,3,4,4-pentachlorobutadienyl)-L-cysteine (PCBD-NAC). Apical treatment with PCBD-GSH (greater than 20 microM) resulted in cytotoxicity, which could be inhibited by acivicin and aminooxyacetic acid (AOAA), inhibitors of gamma-glutamyltranspeptidase (gamma GT) and beta-lyase respectively. In contrast apical treatment with PCBD-NAC was only toxic at high concentrations (greater than 850 microM), and this effect could hardly be inhibited by AOAA. Basolateral treatment of confluent LLC-PK1 monolayers, grown on porous membranes, with PCBD-GSH gave a much smaller response than apical treatment, consistent with the fact that gamma GT is predominantly present at the apical side. Basolateral treatment even with high concentrations of PCBD-NAC (1.1 mM) did not show an increase in cytotoxicity when compared to the effect after apical treatment. These results suggest the absence of an organic anion transporter, by which these conjugates in vivo are transported into the cells from the basolateral side. This supposition was substantiated in a study of transcellular transport of the model ions tetraethyl ammonium (TEA) and para-aminohippurate (PAH), in LLC-PK1 monolayers, grown as indicated above. No active PAH transport could be demonstrated, whereas an active TEA transport was present. The absence of an organic anion transporter limits the usefulness of LLC-PK1 cells for the study of nephrotoxicity of compounds, like PCBD-NAc, needing this transport to enter the cells. However, the finding of an active basolateral organic cation transporter, together with the presence of gamma GT, dipeptidase and beta-lyase, makes this system especially interesting for testing all compounds that use this transporter or these enzymes in order to elicit toxicity.

Topics: Acetylcysteine; Aminooxyacetic Acid; Animals; Anion Transport Proteins; Anions; Biological Transport; Butadienes; Carrier Proteins; Cations; Cell Line; Cell Survival; Epithelial Cells; Epithelium; Glutathione; Isoxazoles; Kidney; Kidney Diseases; p-Aminohippuric Acid; Swine; Tetraethylammonium; Tetraethylammonium Compounds

The nephrotoxicity of hexachloro-1,3-butadiene (HCBD), its glutathione conjugate (HCBD-GSH), cysteine conjugate (HCBD-CYS), and its N-acetyl cysteine conjugate (HCBD-NAC) were compared in male and female Alderley Park rats. Rats, six to eight weeks of age, were given a single intra-peritoneal injection of HCBD or its conjugates and killed 24 hours later. Nephrotoxicity was assessed by histological examination and plasma urea. All three glutathione-derived conjugates produced an elevation of plasma urea and proximal renal tubular necrosis with a similar localization in the pars recta as seen with HCBD. All the conjugates were more nephrotoxic than HCBD itself. HCBD was about four times more toxic to female rats than males. This sex difference was also shown by all the HCBD metabolites.

Topics: Acetylcysteine; Animals; Butadienes; Cysteine; Female; Glutathione; Kidney Diseases; Kidney Medulla; Kidney Tubules, Proximal; Male; Necrosis; Rats; Sex Factors; Urea