AJP - Endocrinology and Metabolism, Vol 242, Issue 5 323-E329, Copyright © 1982 by American Physiological Society
Modulation by adrenalectomy and fasting of insulin effects in perfused hindlimb muscle
H. Shikama, D. T. Chu and J. H. Exton
Perfused hindlimb muscle from fed adrenalectomized rats accumulated more
2-deoxyglucose at submaximal concentrations of insulin in comparison to
muscle from fed normal rats. However, in the fasted state,
insulin-stimulated 2-deoxyglucose uptake was largely inhibited by
adrenalectomy. Basal 2-deoxyglucose uptake did not differ between fed and
fasted normal or adrenalectomized rats. The changes in insulin effects
caused by adrenalectomy were due to altered hexose transport as shown by
measurements of 3-O-methylglucose uptake and of intracellular free and
phosphorylated 2-deoxyglucose. Muscles of fasted normal and fed or fasted
adrenalectomized rats showed higher basal glycogen synthase
--glucose-6-P/+glucose-6-P activity ratios than those of fed normal rats
probably because of decreased glycogen content. However, muscles from fed
or fasted adrenalectomized rats did not show any alterations in insulin
effects on the activity ratio and half-maximal activation constant (A0.5)
for glucose-6-P of glycogen synthase. Because of the dissociation of the
effects of insulin on hexose transport and glycogen synthase in muscle of
fasted adrenalectomized rats, it is concluded that the impairment in
insulin-stimulated hexose transport in these animals is due to a defect
lying beyond the interaction of insulin with its receptor.
