T. Sekine et al., CLONING, FUNCTIONAL-CHARACTERIZATION, AND LOCALIZATION OF A RAT RENALNA-DICARBOXYLATE TRANSPORTER(), American journal of physiology. Renal, fluid and electrolyte physiology, 44(2), 1998, pp. 298-305
We report here the isolation, functional characterization, tissue dist
ribution, and membrane localization of rat renal Na+-dicarboxylate tra
nsporter (rNaDC-1). rNaDC-1 consists of 2,245 nucleotides, and the ded
uced amino acid sequence showed 73% and 75% identity to rabbit and hum
an NaDC-1, respectively. When expressed in Xenopus laevis oocytes, rNa
DC-1 mediated sodium-dependent uptake of di- and tricarboxylates. Subs
trates of rNaDC-1 evoked inward currents in oocytes expressed with rNa
DC-1; succinate, alpha-ketoglutarate, and glutarate were relatively hi
gh-affinity substrates, and citrate was a low-affinity substrate of rN
aDC-1. The coupling ratio of citrate to charge was determined to be 1:
1 at pH 7.4; influx of one positive charge per citrate molecule sugges
ts a symport of three Na+ with a divalent citrate. Expression of rNaDC
-1 mRNA was detected in the kidney and the small and large intestines.
Immunohistochemistry using polyclonal antibodies raised against the 1
4 amino acids at the COOH terminus of rNaDC-1 revealed that rNaDC-1 is
localized exclusively in the luminal membrane of S2 and S3.