INSULIN REGULATION OF VASCULAR SMOOTH-MUSCLE GLUCOSE-TRANSPORT IN INSULIN-SENSITIVE AND RESISTANT RATS

Previous studies from this laboratory demonstrate insulin regulation o f vascular smooth muscle intracellular calcium transport and of vascul ar tone. Accordingly, we measured insulin regulated glucose transport and GLUT4 protein in aortic tissue from insulin-resistant and sensitiv e rats in order to document classical insulin action in this tissue. W e assessed (via in vitro muscle-bath and perfusion) basal and insulin- stimulated [H-3]-2-deoxyglucose transport in aorta from lean and obese Zucker rats. In the muscle-bath system, insulin significantly stimula ted aortic 2-deoxyglucose transport by 30%, but there was no differenc e in either base-line or insulin-stimulated glucose transport in lean versus obese rats. However, in the perfusion system, in which only the luminal surface of the vessel was exposed, insulin significantly (p < 0.04) stimulated 2-deoxyglucose transport in the aorta of only the le an animals. Western blot analysis demonstrated that aorta from lean an d obese Zucker rats contained substantial concentrations of GLUT4 prot ein. Surprisingly, in the muscle-bath system 2-deoxyglucose transport was markedly higher in the aorta than in the soleus (p < 0.0002). Thes e data demonstrate that vascular smooth muscle is an insulin-sensitive tissue which may be partially impaired in insulin resistant animals.