EFFECTS OF STREPTOZOTOCIN-INDUCED DIABETES ON GLUCOSE-TRANSPORT IN SKELETAL-MUSCLE

Female Sprague-Dawley rats were injected with streptozotocin (45 mg/kg) to induce mild diabetes (glucose, >13 mM). Half of the animals received daily insulin injections to reduce hyperglycemia. After 10 weeks, sarcolemmal membranes were isolated from hindlimb muscles to study glucose transport, and the number of glucose transporters was assessed by cyto-chalasin-β binding. Both glucose transport (19.2 ± 1.6 vs. 31.93 ±3.29 pmol/mg protein · 15 sec) and cytochalasin-β binding (3.06 ± 0.28 vs. 6.14 ± 0.59 pmol/mg protein) were significantly (P < 0.05) reduced in the diabetic untreated rats compared to control values. Daily insulin injections restored both (P < 0.05) basal transport (33.22 ± 3.62 pmol/mg protein · 15 sec) and cytochal-asin-β binding (5.52 ± 0.66 pmol/mg protein) to control levels. Maximum insulin stimulation (1 U/kg, iv) significantly increased (P < 0.05) both glucose transport (30.18 ± 3.76 vs. 96.48 ± 4.21 pmol/mg protein · 15 sec) and cytochalasin-β binding (4.38 ± 0.29 vs. 9.40 ± 0.42 pmol/mg protein) in the untreated diabetic and control rats. However, the stimulation in the untreated diabetic rats only reached basal control levels, which was signif-icantly (P < 0.05) below the insulin-stimulated value for the controls. In the rats receiving daily insulin injections, maximum insulin stimulation increased (P < 0.05) both glucose transport (58.67 ± 15.24 pmol/mg protein ·15 sec) and cytochalasin-β binding (6.4 ±0.7 pmol/mg protein), but both transport and binding were significantly (P < 0.05) below insulin-stimulated values for the control rats. These data show that insulin deficiency adversely affected the glucose transport system in skeletal muscle. Both basal and maximum insulin-stimulated transport and the number of transport molecules were reduced. Daily insulin treatment corrected some of the defects, but maximum insulin stimulation was still significantly below values for control animals. © 1990 by The Endocrine Society.