Insulin regulation of vascular smooth muscle glucose transport in insulin-sensitive and resistant rats

Previous studies from this laboratory demonstrate insulin regulation of vascular smooth muscle intracellular calcium transport and of vascular tone. Accordingly, we measured insulin regulated glucose transport and GLUT4 protein in aortic tissue from insulin-resistant and sensitive rats in order to document classical insulin action in this tissue. We 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 stimulated aortic 2-deoxyglucose transport by 30%, but there was no difference 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 lean animals. Western blot analysis demonstrated that aorta from lean and obese Zucker rats contained substantial concentrations of GLUT4 protein. Surprisingly, in the muscle-bath system 2-deoxyglucose transport was markedly higher in the aorta than in the soleus (p < 0.0002). These data demonstrate that vascular smooth muscle is an insulin-sensitive tissue which may be partially impaired in insulin resistant animals.