title: The use of potential-sensitive cyanine dye for studying ion-dependent electrogenic renal transport of organic solutes. Spectrophotometric measurements.
abstract: Renal transport of four different categories of organic solutes, namely sugars, neutral amino acids, monocarboxylic acids and dicarboxylic acids, was studied by using the potential-sensitive dye 3,3'-diethyloxadicarbocyanine iodide in purified luminal-membrane and basolateral-membrane vesicles isolated from rabbit kidney cortex. Valinomycin-induced K(+) diffusion potentials resulted in concomitant changes in dye-membrane-vesicle absorption spectra. Linear relationships were obtained between these changes and depolarization and hyperpolarization of the vesicles. Addition of d-glucose, l-phenylalanine, succinate or l-lactate to luminal-membrane vesicles, in the presence of an extravesicular>intravesicular Na(+) gradient, resulted in rapid transient depolarization. With basolateral-membrane vesicles no electrogenic transport of d-glucose or l-phenylalanine was observed. Spectrophotometric competition studies revealed that d-galactose is electrogenically taken up by the same transport system as that for d-glucose, whereas l-phenylalanine, succinate and l-lactate are transported by different systems in luminal-membrane vesicles. The absorbance changes associated with simultaneous addition of d-glucose and l-phenylalanine were additive. The uptake of these solutes was influenced by the presence of Na(+)-salt anions of different permeabilities in the order: Cl(-)>SO(4) (2-)>gluconate. Addition of valinomycin to K(+)-loaded vesicles enhanced uptake of d-glucose and l-phenylalanine in the presence of an extravesicular>intravesicular Na(+) gradient. Gramicidin or valinomycin plus nigericin diminished/abolished electrogenic solute uptake by Na(+)- or Na(+)+K(+)-loaded vesicles respectively. These results strongly support the presence of Na(+)-dependent renal electrogenic transport of d-glucose, l-phenylalanine, succinate and l-lactate in luminal-membrane vesicles.
mesh_terms: D000818:Animals; D000838:Anions / Q000494:pharmacology; D001692:Biological Transport / Q000187:drug effects; D002232:Carbocyanines; D005260:Female; D005947:Glucose / Q000378:metabolism; D066298:In Vitro Techniques; D007668:Kidney / Q000187:drug effects / Q000378:metabolism*; D007773:Lactates / Q000378:metabolism; D019344:Lactic Acid; D008297:Male; D008564:Membrane Potentials / Q000187:drug effects; D010649:Phenylalanine / Q000378:metabolism; D011804:Quinolines; D011817:Rabbits; D013053:Spectrophotometry; D013386:Succinates / Q000378:metabolism; D019802:Succinic Acid; D014634:Valinomycin / Q000494:pharmacology
chemical_list: D000838:Anions; D002232:Carbocyanines; D007773:Lactates; D011804:Quinolines; D013386:Succinates; C018919:3,3'-diethyloxadicarbocyanine; D014634:Valinomycin; D019344:Lactic Acid; D010649:Phenylalanine; D019802:Succinic Acid; D005947:Glucose