title: NH4+ modulates renal tubule amantadine transport independently of intracellular pH changes.
abstract: A bicarbonate-dependent organic cation transporter, unique from rOCT1 and rOCT2, primarily mediates amantadine uptake into renal proximal tubules. We examined whether intracellular pH regulates bicarbonate-dependent amantadine transporter function in these tubules. NH(4)Cl treatment resulted in immediate intracellular alkalinization of tubules for up to 30s followed by gradual acidification that was maximal at 5min. Proximal tubule amantadine uptake was similarly inhibited (60%) by NH(4)Cl during both the early intracellular alkalinization and later acidification phases. Sodium propionate treatment resulted in immediate intracellular acidification of proximal tubules without inhibiting amantadine uptake. NH(4)Cl inhibition of bicarbonate-dependent amantadine uptake was dose-dependent, competitive and sex-dependent. NH(4)Cl, NH(4)NO(3), (NH(4))(2)SO(4) and (NH(4))(2)HPO(4) inhibited amantadine uptake into proximal tubules similarly. NH(4)Cl also stimulated efflux of amantadine and tetraethylammonium from preloaded proximal tubules, suggesting mediation of a facilitated process. These data suggest the potential for direct modulation of organic cation transporters by NH(4)(+) in rat kidney proximal tubules.
authors.affiliation: Department of Pharmacology and Therapeutics, University of Manitoba Winnipeg, Manitoba, Canada R3E 0W3.
authors.forename: Kerry B
authors.initials: KB
authors.lastname: Goralski
authors.forename: Ratna
authors.initials: R
authors.lastname: Bose
authors.forename: Daniel S
authors.initials: DS
authors.lastname: Sitar
mesh_terms: D000547:Amantadine / Q000493:pharmacokinetics*; D000643:Ammonium Chloride / Q000494:pharmacology; D000645:Ammonium Sulfate / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D004305:Dose-Response Relationship, Drug; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007684:Kidney Tubules / Q000378:metabolism*; D007687:Kidney Tubules, Proximal / Q000378:metabolism; D007700:Kinetics; D009566:Nitrates / Q000494:pharmacology; D010710:Phosphates / Q000494:pharmacology; D011422:Propionates / Q000494:pharmacology; D000644:Quaternary Ammonium Compounds / Q000494:pharmacology*; D051381:Rats; D019789:Tetraethylammonium / Q000493:pharmacokinetics; D013997:Time Factors
chemical_list: D001639:Bicarbonates; D009566:Nitrates; D010710:Phosphates; D011422:Propionates; D000644:Quaternary Ammonium Compounds; C024788:ammonium phosphate; D000643:Ammonium Chloride; D019789:Tetraethylammonium; D000547:Amantadine; C514135:sodium propionate; D000645:Ammonium Sulfate; C006568:ammonium nitrate