Hormonal regulation of glucose transport in contracting skeletal muscle from normal and diabetic rats.

Using the hindlimb perfusion system, we have studied glycogenolysis and glucose transport in resting and contracting skeletal muscle from normal and diabetic rats. Glucose transport was measured using the glucose analogue 2-deoxyglucose. The muscles were treated for 15 minutes with either saline solution, insulin (1 mU/mL) or epinephrine (10(-7) mol/L) at rest and during electrical stimulation. In the resting muscle, basal glycogen was lower in diabetic rats (25 v 40 mumol/g), was not affected by insulin in either group, and was decreased by epinephrine in normal rats (to 26 mumol/g) but not in diabetic rats. Basal glucose transport was identical in the two groups (7.5 mumol/100 g/minute), was stimulated by insulin to a greater extent in diabetics (fivefold) than in normal rats (threefold), but was unaffected by epinephrine in either group. In contracting muscle, glycogen was decreased by 10 mumol/g in normal and diabetic rats independently of hormonal treatment. Basal glucose transport was not affected by muscle contraction with or without epinephrine, whereas the stimulatory effect of insulin on this process was blunted by such contraction (result, 10 mumoles/100 g/minute). We conclude that in normal and diabetic rats, muscle contraction stimulates glycogen breakdown independently of hormonal treatment; muscle contraction per se does not increase glucose transport; and finally, contracting muscle uses glycogen rather than circulating glucose as energy substrate.