Detailed mapping of ochratoxin a reabsorption along the rat nephron in vivo: The nephrotoxin can be reabsorbed in all nephron segments by different mechanisms

Anke Dahlmann, William H Dantzler, Stefan Silbernagl, Michael Gekle

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Abstract

Ochratoxin A (OTA) is a widespread nephrotoxin excreted to a substantial degree via the kidney. Previously we showed that [3H]OTA can be reabsorbed along the rat nephron in vivo (Zingerie et al., 1997). In this study we investigated in detail the contribution of different nephron segments to [3H]OTA reabsorption and determined the possible mechanisms involved by microinfusion and microperfusion experiments. At pH 6 (~94% of OTA neutral), OTA is reabsorbed in all nephron segments investigated. The estimated fractional reabsorptions (FR) at a tubular load of 20 fmol/min are: proximal convoluted tubule (PCT), 14.8%; proximal straight tubule (PST), 27.4%; ascending limb of Henle's loop (ALH), 13,6%; distal tubule (DT), 11.6%; collecting duct (CD), 24.6%; terminal CD, 22.0%. At pH 8 (~10% of OTA neutral) FR are as follows: PCT, 0%; PST, 25.9%; ALH, 14.0%; DT, 3.2%; CD, 8.2%. Thus, OTA reabsorption in PST and ALH is pH-independent. Reabsorption in PST but not in DT or CD was inhibited by sulfobromophthalein, a substrate of the apical organic anion carder. L-Phenylalanine did not reduce OTA reabsorption. After intravenous injection of unlabeled OTA, resulting in a plasma concentration of ~10-5 mol/l, the FR of [3H]OTA during early proximal microinfusion was reduced slightly. From our results we conclude: 1) OTA can be reabsorbed in all nephron segments investigated. 2) Under physiological conditions the predominant sites of reabsorption are PST, ALH and terminal CD. 3) Reabsorption in PST and ALH is not pH-dependent. 4) pH- independent reabsorption in PST is mediated by the apical organic anion transporter (OAT-K1), whereas pH-dependent reabsorption in PCT is mediated by H+-dipeptide cotransporter(s). 5) Reabsorption also takes place during natural exposure, i.e., when OTA is present in plasma and renal tissue. 6) The high FR in ALH and CD explains, at least in part, the preferential impairment of postproximal functions and the accumulation in renal inner medulla and papilla.

Original languageEnglish (US)
Pages (from-to)157-162
Number of pages6
JournalJournal of Pharmacology and Experimental Therapeutics
Volume286
Issue number1
StatePublished - Jul 1998

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Ochratoxins
Nephrons
Loop of Henle
Kidney
ochratoxin A
Organic Anion Transporters
Sulfobromophthalein
Dipeptides
Phenylalanine
Intravenous Injections
Anions

ASJC Scopus subject areas

  • Pharmacology

Cite this

@article{fa2e7bbd12b64490b074a217a9ecb79d,
title = "Detailed mapping of ochratoxin a reabsorption along the rat nephron in vivo: The nephrotoxin can be reabsorbed in all nephron segments by different mechanisms",
abstract = "Ochratoxin A (OTA) is a widespread nephrotoxin excreted to a substantial degree via the kidney. Previously we showed that [3H]OTA can be reabsorbed along the rat nephron in vivo (Zingerie et al., 1997). In this study we investigated in detail the contribution of different nephron segments to [3H]OTA reabsorption and determined the possible mechanisms involved by microinfusion and microperfusion experiments. At pH 6 (~94{\%} of OTA neutral), OTA is reabsorbed in all nephron segments investigated. The estimated fractional reabsorptions (FR) at a tubular load of 20 fmol/min are: proximal convoluted tubule (PCT), 14.8{\%}; proximal straight tubule (PST), 27.4{\%}; ascending limb of Henle's loop (ALH), 13,6{\%}; distal tubule (DT), 11.6{\%}; collecting duct (CD), 24.6{\%}; terminal CD, 22.0{\%}. At pH 8 (~10{\%} of OTA neutral) FR are as follows: PCT, 0{\%}; PST, 25.9{\%}; ALH, 14.0{\%}; DT, 3.2{\%}; CD, 8.2{\%}. Thus, OTA reabsorption in PST and ALH is pH-independent. Reabsorption in PST but not in DT or CD was inhibited by sulfobromophthalein, a substrate of the apical organic anion carder. L-Phenylalanine did not reduce OTA reabsorption. After intravenous injection of unlabeled OTA, resulting in a plasma concentration of ~10-5 mol/l, the FR of [3H]OTA during early proximal microinfusion was reduced slightly. From our results we conclude: 1) OTA can be reabsorbed in all nephron segments investigated. 2) Under physiological conditions the predominant sites of reabsorption are PST, ALH and terminal CD. 3) Reabsorption in PST and ALH is not pH-dependent. 4) pH- independent reabsorption in PST is mediated by the apical organic anion transporter (OAT-K1), whereas pH-dependent reabsorption in PCT is mediated by H+-dipeptide cotransporter(s). 5) Reabsorption also takes place during natural exposure, i.e., when OTA is present in plasma and renal tissue. 6) The high FR in ALH and CD explains, at least in part, the preferential impairment of postproximal functions and the accumulation in renal inner medulla and papilla.",
author = "Anke Dahlmann and Dantzler, {William H} and Stefan Silbernagl and Michael Gekle",
year = "1998",
month = "7",
language = "English (US)",
volume = "286",
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TY - JOUR

T1 - Detailed mapping of ochratoxin a reabsorption along the rat nephron in vivo

T2 - The nephrotoxin can be reabsorbed in all nephron segments by different mechanisms

AU - Dahlmann, Anke

AU - Dantzler, William H

AU - Silbernagl, Stefan

AU - Gekle, Michael

PY - 1998/7

Y1 - 1998/7

N2 - Ochratoxin A (OTA) is a widespread nephrotoxin excreted to a substantial degree via the kidney. Previously we showed that [3H]OTA can be reabsorbed along the rat nephron in vivo (Zingerie et al., 1997). In this study we investigated in detail the contribution of different nephron segments to [3H]OTA reabsorption and determined the possible mechanisms involved by microinfusion and microperfusion experiments. At pH 6 (~94% of OTA neutral), OTA is reabsorbed in all nephron segments investigated. The estimated fractional reabsorptions (FR) at a tubular load of 20 fmol/min are: proximal convoluted tubule (PCT), 14.8%; proximal straight tubule (PST), 27.4%; ascending limb of Henle's loop (ALH), 13,6%; distal tubule (DT), 11.6%; collecting duct (CD), 24.6%; terminal CD, 22.0%. At pH 8 (~10% of OTA neutral) FR are as follows: PCT, 0%; PST, 25.9%; ALH, 14.0%; DT, 3.2%; CD, 8.2%. Thus, OTA reabsorption in PST and ALH is pH-independent. Reabsorption in PST but not in DT or CD was inhibited by sulfobromophthalein, a substrate of the apical organic anion carder. L-Phenylalanine did not reduce OTA reabsorption. After intravenous injection of unlabeled OTA, resulting in a plasma concentration of ~10-5 mol/l, the FR of [3H]OTA during early proximal microinfusion was reduced slightly. From our results we conclude: 1) OTA can be reabsorbed in all nephron segments investigated. 2) Under physiological conditions the predominant sites of reabsorption are PST, ALH and terminal CD. 3) Reabsorption in PST and ALH is not pH-dependent. 4) pH- independent reabsorption in PST is mediated by the apical organic anion transporter (OAT-K1), whereas pH-dependent reabsorption in PCT is mediated by H+-dipeptide cotransporter(s). 5) Reabsorption also takes place during natural exposure, i.e., when OTA is present in plasma and renal tissue. 6) The high FR in ALH and CD explains, at least in part, the preferential impairment of postproximal functions and the accumulation in renal inner medulla and papilla.

AB - Ochratoxin A (OTA) is a widespread nephrotoxin excreted to a substantial degree via the kidney. Previously we showed that [3H]OTA can be reabsorbed along the rat nephron in vivo (Zingerie et al., 1997). In this study we investigated in detail the contribution of different nephron segments to [3H]OTA reabsorption and determined the possible mechanisms involved by microinfusion and microperfusion experiments. At pH 6 (~94% of OTA neutral), OTA is reabsorbed in all nephron segments investigated. The estimated fractional reabsorptions (FR) at a tubular load of 20 fmol/min are: proximal convoluted tubule (PCT), 14.8%; proximal straight tubule (PST), 27.4%; ascending limb of Henle's loop (ALH), 13,6%; distal tubule (DT), 11.6%; collecting duct (CD), 24.6%; terminal CD, 22.0%. At pH 8 (~10% of OTA neutral) FR are as follows: PCT, 0%; PST, 25.9%; ALH, 14.0%; DT, 3.2%; CD, 8.2%. Thus, OTA reabsorption in PST and ALH is pH-independent. Reabsorption in PST but not in DT or CD was inhibited by sulfobromophthalein, a substrate of the apical organic anion carder. L-Phenylalanine did not reduce OTA reabsorption. After intravenous injection of unlabeled OTA, resulting in a plasma concentration of ~10-5 mol/l, the FR of [3H]OTA during early proximal microinfusion was reduced slightly. From our results we conclude: 1) OTA can be reabsorbed in all nephron segments investigated. 2) Under physiological conditions the predominant sites of reabsorption are PST, ALH and terminal CD. 3) Reabsorption in PST and ALH is not pH-dependent. 4) pH- independent reabsorption in PST is mediated by the apical organic anion transporter (OAT-K1), whereas pH-dependent reabsorption in PCT is mediated by H+-dipeptide cotransporter(s). 5) Reabsorption also takes place during natural exposure, i.e., when OTA is present in plasma and renal tissue. 6) The high FR in ALH and CD explains, at least in part, the preferential impairment of postproximal functions and the accumulation in renal inner medulla and papilla.

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