Comparison of the transcellular transport of FDG and D-glucose by the kidney epithelial cell line, LLC-PK1.
OBJECTIVE
Almost all D-glucose (GLU) filtered through the glomerulus is reabsorbed by the renal proximal tubules, whereas a high portion of 2-[18F]fluoro-2-deoxy-D-glucose [(18F)FDG] is excreted through the urine. However, [18F]FDG is not entirely excreted in the urine suggesting that it may be partially reabsorbed by the proximal tubules. The purpose of this study was to compare the time course of transcellular transport of administered [14C] labeled FDG ([14C]FDG) with that of [14C] labeled GLU ([14C]GLU) using the kidney epithelial cell line, LLC-PK1.


METHODS
Transcellular transport of [14C]FDG and [14C]GLU by LLC-PK1 cells was measured in Na+-containing or Na+-free Dulbecco's phosphate-buffered saline [PBS(+) and PBS(-), respectively] in the presence or absence of phlorizin, phloretin, probenecid, or tetraethylammonium bromide inhibitors that predominantly inhibit sodium-dependent glucose transporters (SGLTs), sodium-independent glucose transporters, organic anion transporters, and organic cation transporters, respectively.


RESULTS
When assayed in PBS(+), less [14C]FDG than [14C]GLU was reabsorbed by the proximal tubular cells over the entire incubation time. Reabsorption of [14C]FDG was mediated mainly by SGLT at early time points in the incubation, whereas high reabsorption of [14C]GLU was mediated by both SGLT and glucose transporter over 90 min of incubation. Secretion of [14C]FDG also tended to be slightly higher than that of [14C]GLU over 90 min of incubation.


CONCLUSIONS
Transcellular transport of [14C]FDG over time by LLC-PK1 cells was clarified. The polarized distribution of transcellular transporters of [14C]FDG and [14C]GLU in LLC-PK1 cells differs.
Kobayashi
Masato
M
Graduate School of Medical Science, Kanazawa University, Kanazawa, Ishikawa, Japan.
Shikano
Naoto
N
Nishii
Ryuichi
R
Kiyono
Yasushi
Y
Araki
Hiroyo
H
Nishi
Kodai
K
Oh
Myungmi
M
Okudaira
Hiroyuki
H
Ogura
Masato
M
Yoshimoto
Mitsuyoshi
M
Okazawa
Hidehiko
H
Fujibayashi
Yasuhisa
Y
Kawai
Keiichi
K
D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D004847:Epithelial Cells / Q000187:drug effects / Q000378:metabolism*; D019788:Fluorodeoxyglucose F18 / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism*; D051246:Glucose Transport Proteins, Facilitative / Q000037:antagonists & inhibitors / Q000378:metabolism; D007668:Kidney / Q000166:cytology*; D007687:Kidney Tubules, Proximal / Q000166:cytology; D027361:Organic Anion Transporters / Q000378:metabolism; D027701:Organic Cation Transport Proteins / Q000378:metabolism; D011868:Radioisotopes; D051247:Sodium-Glucose Transport Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism; D013997:Time Factors
D051246:Glucose Transport Proteins, Facilitative; D027361:Organic Anion Transporters; D027701:Organic Cation Transport Proteins; D011868:Radioisotopes; D051247:Sodium-Glucose Transport Proteins; D019788:Fluorodeoxyglucose F18; D005947:Glucose