AJP - Cell Physiology, Vol 259, Issue 2 286-C294, Copyright © 1990 by American Physiological Society
Differential localization of two glucose transporter isoforms in rat kidney
B. Thorens, H. F. Lodish and D. Brown
Whitehead Institute for Biomedical Research, Cambridge, Massachusetts 02142.
The localization of two glucose transporter isoforms was mapped in the rat
kidney: the high-Michaelis constant (Km; 15-20 mM) low-affinity "liver"
transporter and the low-Km (1-2 mM) high-affinity "erythroid/brain"
transporter. Both are basolateral membrane proteins, but the liver
transporter was present exclusively in the S1 part of the proximal tubule,
whereas the erythroid/brain transporter was expressed at variable levels in
different nephron segments. Staining intensity was low in the straight
proximal tubule (S3), intermediate in the medullary thin and thick
ascending limbs, and highest in connecting segments and collecting ducts.
In the collecting duct, the erythroid/brain glucose transporter was
expressed at the highest level in intercalated cells; less was present in
principal cells. In the papilla, only intercalated cells expressed this
transporter isoform. These results suggest specific involvements of each
transporter isoform in transepithelial glucose reabsorption by different
segments of the proximal tubule. They also indicate that while the liver
glucose transporter is present in gluconeogenic cells, there is a good
correlation between the level of expression of the erythroid/brain glucose
transporter and the glycolytic activity of the different nephron segments.
