We have characterized the glucose-transport system in soleus muscle from fe
male GLUT4-null mice to determine whether GLUT1, 3 or 5 account for insulin
-stimulated glucose-transport activity. Insulin increased 2-deoxyglucose up
take 2.8- and 2.1-fold in soleus muscle from wild-type and GLUT4-null mice,
respectively. Cytochalasin B, an inhibitor of GLUT1- and GLUT4-mediated gl
ucose transport, inhibited insulin-stimulated 2-deoxyglucose uptake by > 95
% in wild-type and GLUT4-null soleus muscle. Addition of 35 mM fructose to
the incubation media was without effect on insulin-stimulated 3-O-methyl-gl
ucose transport activity in soleus muscle from either genotype, whereas 35
mM glucose inhibited insulin-stimulated (20 nM) 3-O-methylglucose transport
by 65% in wild-type and 99% in GLUT4-null mice. We utilized the 2-N-4-1-(1
-azi-2,2,2-trifluoroethyl)benzoyl-1,3-bis(D-mannose-4-yloxy)-2-propylamine
(ATB-BMPA) exofacial photolabel to determine if increased cell-surface GLUT
1 or GLUT4 content accounted for insulin-stimulated glucose transport in GL
UT4-null muscle. In wild-type soleus muscle, cell-surface GLUT4 content was
increased by 2.8-fold under insulin-stimulated conditions and this increas
e corresponded to the increase in 2-deoxyglucose uptake. No detectable cell
-surface GLUT4 was observed in soleus muscle from female GLUT4-null mice un
der either basal or insulin-stimulated conditions. Basal cell-surface GLUT1
content was similar between wild-type and GLUT4-null mice, with no further
increase noted in either genotype with insulin exposure. Neither GLUT3 nor
GLUTS appeared to account for insulin-stimulated glucose-transport activit
y in wild-type or GLUT4-null muscle. In conclusion, insulin-stimulated gluc
ose-transport activity in female GLUT4-null soleus muscle is mediated by a
facilitative transport process that is glucose- and cytochalasin B-inhibita
ble, but which is not labelled strongly by ATB-BMPA.