1. ¹Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Concepción, Chile
2. ²Departamento de Biología Celular, Facultad de Ciencias, Universidad de Málaga, Málaga, Spain
3. ³Instituto de Bioquímica, Facultad de Ciencias Biológicas, Universidad Austral de Chile, Valdivia, Chile
4. ⁴Instituto de Anatomía, Histología y Patología, Facultad de Medicina, Universidad Austral de Chile, Valdivia, Chile

Correspondence: Francisco Nualart, Departamento de Biología Celular, Facultad de Ciencias Biológicas, Universidad de Concepción, Casilla, Concepción 160-C, Chile. E-mail: frnualart@udec.cl

Received 28 December 2007; Revised 2 April 2008; Accepted 29 April 2008; Published online 9 July 2008.

Abstract

Vitamin C is reabsorbed from the renal lumen by one isoform of sodium-vitamin C co-transporters that mediate high affinity sodium-dependent L-ascorbic acid transport. Sodium-vitamin C cotransporter-1 mRNA has been detected in intestine and liver and the S3 segment of the renal proximal tubule. Here, we found that its distribution was broader and all three proximal tubule segments of mouse and human expressed the transporter but the S3 segment had the highest expression. Sodium-vitamin C co-transporter-1 expression was also found in the renal epithelial-derived LLC-PK1 cell line. Ascorbic acid transport in these cells was regulated by a single kinetic component that depended on the sodium concentration, pH and temperature. Reducing ascorbate concentration increased the apical expression of the transporter suggesting the presence of a feedback system for regulation of transporter abundance at the luminal membrane.