Mj. Duclos et al., INSULIN-LIKE GROWTH FACTOR-I-STIMULATED GLUCOSE-TRANSPORT IN MYOTUBESDERIVED FROM CHICKEN MUSCLE SATELLITE CELLS, Journal of Endocrinology, 137(3), 1993, pp. 465-472
The effects of insulin and insulin-like growth factor-I (IGF-1) on glu
cose transport were compared in myotubes derived from chicken breast m
uscle satellite cells in vitro. Myotubes were incubated (for 0.5 or 4
h) with or without glucose in the presence or absence of insulin or IG
F-I. Glucose uptake was subsequently measured by the incorporation of
2-[1,2-H-3(N)] deoxy-D-glucose ([H-3]2DG) in glucose-free medium (10 m
in at 20-degrees-C). Glucose uptake was almost completely abolished by
the addition of cytochalasin B or phloretin. It was increased by a de
crease in glucose concentration in the incubation medium. Insulin (5 m
g/1) stimulated [H-3]2DG uptake to a maximum of 43 +/- 10% above basal
after 30-min incubation and 101 +/- 15% after 4-h incubation. IGF-I a
nd insulin at equimolar concentrations (25 mug/l and 20 mug/l respecti
vely) were almost equipotent after 0.5 h but after 4-h incubation IGF-
I was 17-fold more potent, suggesting that this 'late' effect was medi
ated through the IGF-I receptor. Incubation with cycloheximide suggest
ed that the effect of IGF-I involved increased protein synthesis. The
results suggest that chicken myotubes express a glucose transporter wh
ich is regulated by IGF-I and glucose concentration. However, they do
not appear to express a typical insulin-responsive transport s stem.