title: Characteristics of D-alanine transport by luminal membrane vesicles from pars convoluta and pars recta of rabbit proximal tubule.
abstract: Uptake of D-alanine against a concentration gradient has been shown to occur with isolated luminal-membrane vesicles from pars convoluta or pars recta of rabbit proximal tubule. Renal D-alanine transport systems, displaying the following characteristics, were shown: (1) In vesicles from pars convoluta, the uptake of D-alanine was mediated by both Na+-dependent and Na+-independent transport processes. It was found that an inwardly directed H+-gradient could drive the transport of D-alanine into the vesicles both in the presence and absence of Na+. Thus, in addition to Na+, the transport of D-alanine is influenced by the H+-gradient. (2) In vesicles from pars recta, the transient accumulation of D-alanine was strictly dependent on Na+, since no 'overshoot' was ever observed in the absence of Na+. Although the Na+-dependent uptake of D-alanine was stimulated at acid pH, H+ did not substitute for Na+, as it apparently does in pars convoluta, but instead potentiated the Na+ effect. (3) Addition of L-alanine to vesicle preparations, both from pars convoluta and from pars recta, specifically inhibited renal uptake of D-alanine. A comparison between the transport characteristics of D- and L-alanine indicated that these two isomers of alanine probably share common transport systems located along the proximal tubule of rabbit kidney.
authors.affiliation: Institute of Medical Biochemistry, University of Aarhus, Denmark.
authors.forename: H
authors.initials: H
authors.lastname: Jessen
authors.forename: H
authors.initials: H
authors.lastname: Vorum
authors.forename: K E
authors.initials: KE
authors.lastname: Jørgensen
authors.forename: M I
authors.initials: MI
authors.lastname: Sheikh
mesh_terms: D000409:Alanine / Q000493:pharmacokinetics*; D000818:Animals; D001693:Biological Transport, Active; D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone / Q000494:pharmacology; D005947:Glucose / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007536:Isomerism; D007687:Kidney Tubules, Proximal / Q000378:metabolism* / Q000648:ultrastructure; D011817:Rabbits; D012964:Sodium / Q000378:metabolism
chemical_list: D002259:Carbonyl Cyanide p-Trifluoromethoxyphenylhydrazone; D012964:Sodium; D005947:Glucose; D000409:Alanine