Transport and activation of S-(1,2-dichlorovinyl)-L-cysteine and N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine in rat kidney proximal tubules

Journal Article · Tue Aug 01 04:00:00 EDT 1989 · Toxicology and Applied Pharmacology; (USA)

DOI:https://doi.org/10.1016/0041-008X(89)90091-4· OSTI ID:5606203

Zhang, G H; Stevens, J L ^[1]

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1. W. Alton Jones Cells Science Center, Lake Placid, NY (USA)

An important step in understanding the mechanism underlying the tubular specificity of the nephrotoxicity of toxic cysteine conjugates is to identify the rate-limiting steps in their activation. The rate-limiting steps in the activation of toxic cysteine conjugates were characterized using isolated proximal tubules from the rat and 35S-labeled S-(1,2-dichlorovinyl)-L-cysteine (DCVC) and N-acetyl-S-(1,2-dichlorovinyl)-L-cysteine (NAC-DCVC) as model compounds. The accumulation by tubules of 35S radiolabel from both DCVC and NAC-DCVC was time and temperature dependent and was mediated by both Na+-dependent and independent processes. Kinetic studies with DCVC in the presence of sodium revealed the presence of two components with apparent Km and Vmax values of (1) 46 microM and 0.21 nmol/mg min and (2) 2080 microM and 7.3 nmol/mg.min. NAC-DVVC uptake was via a single system with apparent Km and Vmax values of 157 microM and 0.65 nmol/mg.min, respectively. Probenecid, an inhibitor of the renal organic anion transport system, inhibited accumulation of radiolabel from NAC-DCVC, but not from DCVC. The covalent binding of 35S label to cellular macromolecules was much greater from (35S)DCVC than from NAC-(35S)DCVC. Analysis of metabolites showed that a substantial amount of the cellular NAC-(35S)DCVC was unmetabolized while (35S)DCVC was rapidly metabolized to bound 35S-labeled material and unidentified products. The data suggest that DCVC is rapidly metabolized following transport, but that activation of NAC-DCVC depends on a slower rate of deacetylation. The results are discussed with regard to the segment specificity of cysteine conjugate toxicity and the role of disposition in vivo in the nephrotoxicity of glutathione conjugates.

• OSTI ID: 5606203
• Journal Information: Toxicology and Applied Pharmacology; (USA), Journal Name: Toxicology and Applied Pharmacology; (USA) Vol. 100:1; ISSN TXAPA; ISSN 0041-008X
• Country of Publication: United States
• Language: English

Related Subjects

550501* -- Metabolism-- Tracer Techniques
59 BASIC BIOLOGICAL SCIENCES
AMINO ACIDS
ANIMALS
BETA DECAY RADIOISOTOPES
BETA-MINUS DECAY RADIOISOTOPES
BIOCHEMICAL REACTION KINETICS
BODY
CARBOXYLIC ACIDS
CYSTEINE
DAYS LIVING RADIOISOTOPES
EVEN-ODD NUCLEI
IN VITRO
ISOTOPE APPLICATIONS
ISOTOPES
KIDNEYS
KINETICS
LIGHT NUCLEI
MAMMALS
MEMBRANE TRANSPORT
METABOLISM
NUCLEI
ORGANIC ACIDS
ORGANIC COMPOUNDS
ORGANIC SULFUR COMPOUNDS
ORGANS
RADIOISOTOPES
RATS
REACTION KINETICS
RODENTS
SULFUR 35
SULFUR ISOTOPES
TEMPERATURE DEPENDENCE
THIOLS
TIME DEPENDENCE
TOXICITY
TRACER TECHNIQUES
TUBULES
VERTEBRATES