Interaction of the metal chelator 2,3-dimercapto-1-propanesulfonate with the rabbit multispecific organic anion transporter 1 (rbOAT1)

Mol Pharmacol. 2002 Nov;62(5):1128-36. doi: 10.1124/mol.62.5.1128.

Abstract

The metal chelator DMPS (2,3-dimercapto-1-propanesulfonate) is used to treat heavy metal intoxication because it increases renal excretion of these toxins, which are accumulated in proximal tubule cells. To evaluate the involvement of the organic anion transporter 1 (OAT1) in the renal flux of DMPS, we examined the effect of DMPS on transport mediated by the rabbit ortholog of OAT1 and compared these characteristics with those observed in intact isolated rabbit proximal tubules. The rabbit OAT1 (rbOAT1) cDNA consisted of 2124 base pairs encoding a protein of 551 amino acids. Heterologous expression in COS-7 cells revealed rbOAT1-mediated transport of p-aminohippurate (PAH; K(t) = 16 microM). A 1 mM concentration of unlabeled PAH, alpha-ketoglutarate, urate, or probenecid inhibited [(3)H]PAH uptake by 70 to 90%. cis-Inhibition and trans-stimulation experiments using several Krebs cycle intermediates implicated alpha-ketoglutarate as the main intracellular exchange anion. Reduced DMPS inhibited rbOAT1-mediated fluorescein transport with an apparent K(i) of 102 microM. These characteristics paralleled those observed in isolated rabbit proximal tubules. PAH was transported into nonperfused single proximal tubule S(2) segments with a K(t) of 76 microM. DMPS inhibited FL uptake into single tubule segments with a K(i-app) of 71 microM. Fluorescein efflux from preloaded tubules was trans-stimulated by 1 mM PAH and 1 mM DMPS, consistent with DMPS entry into tubule cells by rbOAT1. In summary, rbOAT1 mediates basolateral uptake of DMPS into proximal tubule cells, implicating this process in the detoxification process of heavy metals in the kidneys.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Amino Acid Sequence
  • Animals
  • Anions / metabolism
  • COS Cells
  • Chelating Agents / pharmacology*
  • Cloning, Molecular
  • Haplorhini
  • Kidney Tubules, Proximal / drug effects
  • Kidney Tubules, Proximal / metabolism
  • Molecular Sequence Data
  • Organic Anion Transport Protein 1 / drug effects*
  • Organic Anion Transport Protein 1 / genetics
  • Organic Anion Transport Protein 1 / metabolism
  • Rabbits
  • Sequence Homology, Amino Acid
  • Unithiol / pharmacology*
  • p-Aminohippuric Acid / pharmacology

Substances

  • Anions
  • Chelating Agents
  • Organic Anion Transport Protein 1
  • Unithiol
  • p-Aminohippuric Acid