Diabetes, Vol 39, Issue 4 441-446, Copyright © 1990 by American Diabetes Association
Increased liver glucose-transporter protein and mRNA in streptozocin-induced diabetic rats
Y Oka, T Asano, Y Shibasaki, JL Lin, K Tsukuda, Y Akanuma and F Takaku
Third Department of Internal Medicine, Faculty of Medicine, University of Tokyo, Hongo, Japan.
The effect of insulin-deficient diabetic states on the rat liver
glucose-transporter (L-transporter isoform) protein and mRNA levels were
studied. Rats were injected with 65 mg/kg streptozocin to induce diabetes
and were maintained for 10 days and then treated with or without insulin
for the next 5 days. The L-transporter isoform with apparent Mr of 55,000
was observed to be increased approximately twofold in the membranes from
liver homogenates of diabetic rats compared with control rats when assessed
by Western blot analysis with an anti-peptide antibody directed against rat
L-transporter isoform. Insulin treatment of diabetic rats decreased the
amount of L-transporter isoform protein toward levels observed in
nondiabetic rats. Northern blot analysis demonstrated similar alterations
in the rat L-transporter isoform mRNA that paralleled the changes observed
in the L-transporter isoform protein. The increased levels of the
L-transporter isoform protein and mRNA in diabetic rats are in marked
contrast to the effects of insulin deficiency in rat adipocytes, which
specifically decrease the amount of the adipocyte glucose-transporter
isoform protein and mRNA. These results suggest that glucose-transporter
isoforms in rat liver and adipocytes are regulated by different mechanisms
and that an increased synthesis of the L-transporter isoform may contribute
to the increased glucose output that occurs from the liver during insulin
deficiency.