Regulation of glucose transport in Clone 9 cells by thyroid hormone.
Triiodothyronine (T3) is found to stimulate cytochalasin B-inhibitable glucose transport in Clone 9 cells, a 'non-transformed' rat liver cell line. After an initial lag period of more than 3 h, glucose transport rate is significantly increased at 6 h and reaches more than 3-times the control rate at 24 h. The enhancement of glucose transport by T3 is due to an increase in transport Vmax and occurs in the absence of a change in either the Km for glucose transport (approximately 3 mM) or the Ki for inhibition of transport by cytochalasin B ((1-2).10(-7) M). Consistent with the observed Ki for cytochalasin B, Northern blot analysis of RNA from control and T3-treated cells employing cDNA probes encoding GTs of the human erythrocyte/rat brain/HepG2 cell transporter (GLUT-1), rat muscle/fat cell transporter (GLUT-4), and rat liver transporter (GLUT-2) types indicates expression of only the GLUT-1 mRNA isoform in these cells. The abundance of GLUT-1 mRNA increases approx. 1.9-fold after 24 h of T3 treatment and is accompanied by an approx. 1.3-fold increase in the abundance of GLUT-1 in whole-cell extracts as demonstrated by Western blot analysis employing a polyclonal antibody directed against the 13 amino acid C-terminal peptide of GLUT-1. The more than 3-fold stimulation of glucose transport at 24 h substantially exceeds the fractional increment in transporter abundance suggesting that, in addition to increasing total GLUT-1 abundance, exposure to T3 may result in a translocation of transporters to the plasma membrane or an activation of pre-existing membrane transporter sites.
Kuruvilla
A K
AK
Department of Medicine, College of Physicians and Surgeons, Columbia University, New York City, NY 10032.
Perez
C
C
Ismail-Beigi
F
F
Loeb
J N
JN
D019325:3-O-Methylglucose; D000818:Animals; D001693:Biological Transport, Active; D015152:Blotting, Northern; D015153:Blotting, Western; D002460:Cell Line; D002462:Cell Membrane / Q000378:metabolism; D005947:Glucose / Q000378:metabolism*; D008757:Methylglucosides / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000378:metabolism; D012313:RNA / Q000378:metabolism; D051381:Rats; D014284:Triiodothyronine / Q000502:physiology*
D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D014284:Triiodothyronine; D019325:3-O-Methylglucose; D012313:RNA; D005947:Glucose