title: The presence of an Na+/spermine antiporter in the rat renal brush-border membrane.
abstract: This study was aimed at determining the driving force for spermine transport in rat renal proximal tubular brush-border membrane. The uptake of spermine and trientine, a spermine-like drug used for treating Wilson's disease, into rat renal brush-border membrane vesicles was significantly stimulated by an outwardly directed Na+ gradient. The Na+-dependent uptake was temperature dependent and saturable. A kinetic analysis of the initial uptake of spermine with an Na+ gradient gave a Km value of 1.44 microM and a Vmax value of 6.31 pmol (mg protein)(-1)/30s. The Na+ dependent uptake of [3H]spermine was inhibited by spermine, trientine and tetraethylene-pentamine. Substrates of the H+/organic cation transporter (cimetidine and tetraethyl-ammonium), physiological polyamines (putrescine and spermidine) with 2 or 3 amino groups and aminoglycosides (amikacin and tobramicin) with 4 or 5 cationic amines did not affect the uptake of spermine in the presence of an outwardly directed Na+ gradient. These results suggest that the renal tubular secretion of spermine is mediated by an Na+/spermine antiport system which is specific for a straight-chain polyamine compound with more than 4 amino groups.
authors.affiliation: Department of Pharmacy, Hokkaido University Hospital, School of Medicine, Hokkaido University, Sapporo, Japan.
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
authors.forename: H
authors.initials: H
authors.lastname: Fujisaki
authors.forename: M
authors.initials: M
authors.lastname: Sugawara
authors.forename: K
authors.initials: K
authors.lastname: Iseki
authors.forename: K
authors.initials: K
authors.lastname: Miyazaki
mesh_terms: D000818:Animals; D017920:Antiporters / Q000502:physiology*; D004347:Drug Interactions; D066298:In Vitro Techniques; D007684:Kidney Tubules / Q000502:physiology*; D008871:Microvilli / Q000737:chemistry* / Q000378:metabolism; D011073:Polyamines / Q000493:pharmacokinetics*; D051381:Rats; D017208:Rats, Wistar; D012964:Sodium / Q000737:chemistry*; D013096:Spermine / Q000493:pharmacokinetics*; D013696:Temperature; D014266:Trientine / Q000493:pharmacokinetics
chemical_list: D017920:Antiporters; D011073:Polyamines; D013096:Spermine; D012964:Sodium; D014266:Trientine