Inhibition of the high-affinity glucose transporter GLUT 1 affects the sensitivity to glucose in a hamster-derived pancreatic beta cell line (HIT).
HIT is a hamster-derived beta-cell line which in contrast to normal beta cells that only express the high Km GLUT-2 glucose transporter, also expresses the low Km glucose transporter GLUT 1. In HIT cells the abnormal glucose transport mechanism is associated with a marked shift to the left of the glucose-induced insulin release dose-response curve. We have used this cell model to investigate whether changes in glucose transport affect the glucose-induced insulin release. HIT cells were first incubated with a concentration of cytochalasin B (0.4 mumol/l) that selectively inhibits the GLUT-1 but not the GLUT-2 transporter. The consequences of blocking glucose phosphorylation and insulin release were studied. Exposure to 0.4 mumol/l cytochalasin B for 1 h caused a selective loss of the low Km transport: the calculated Vmax of GLUT 1 was reduced from 1726 +/- 98 to 184 +/- 14 pmol.mg protein-1 5 min-1 (mean +/- SEM, n = 6, p < 0.005), while no major difference in the high Km (GLUT-2) transport was observed. In cytochalasin B exposed HIT cells the glucose phosphorylating activity (due to hexokinase and glucokinase) was unaffected.(ABSTRACT TRUNCATED AT 250 WORDS)
Rabuazzo
A M
AM
Institute of Internal Medicine, Metabolism and Endocrinology, University of Catania Medical School, Italy.
Buscema
M
M
Vinci
C
C
Caltabiano
V
V
Anello
M
M
Vigneri
R
R
Purrello
F
F
D019325:3-O-Methylglucose; D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002460:Cell Line; D006224:Cricetinae; D003571:Cytochalasin B / Q000494:pharmacology*; D005947:Glucose / Q000378:metabolism* / Q000494:pharmacology*; D051272:Glucose Transporter Type 1; D007328:Insulin / Q000378:metabolism; D000078790:Insulin Secretion; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D007700:Kinetics; D008757:Methylglucosides / Q000378:metabolism; D009004:Monosaccharide Transport Proteins / Q000037:antagonists & inhibitors*
D051272:Glucose Transporter Type 1; D007328:Insulin; D008757:Methylglucosides; D009004:Monosaccharide Transport Proteins; D019325:3-O-Methylglucose; D003571:Cytochalasin B; D005947:Glucose