Effects of insulin on regional blood flow and glucose uptake in Wistar andSprague-Dawley rats

The euglycemic-hyperinsulinemic clamp technique in conscious Sprague-Dawley and Wistar rats chronically instrumented with intravascular catheters and pulsed Doppler flow probes was used to examine insulin's actions on regiona l blood flow and glucose metabolism. The effect of insulin on in vivo and i n vitro glucose utilization in individual muscles was estimated using [H-3] -2-deoxy-D-glucose. We found that in both strains, insulin (4, 32, and 64 m U.kg(-1).min(-1)) causes similar cardiovascular changes characterized by sl ight increases in blood pressure (at high dose), vasodilation in renal and hindquarter vascular beds, and vasoconstriction (at high dose) in the super ior mesenteric vascular bed. However, at the lowest dose of insulin tested, we found a smaller insulin sensitivity index and a lower insulin-stimulate d in vivo glucose uptake in extensor digitorum longus (EDL) muscles of Wist ar versus Sprague-Dawley rats. Higher insulin-stimulated glucose transport activity was found in isolated soleus muscle, while greater basal glucose t ransport was noted in isolated EDL muscle from Sprague-Dawley versus Wistar rats. These results provide further evidence far an insulin blood flow-reg ulatory effect and suggest that strain characteristics (differences in musc le perfusion, hindquarter composition, or fiber insulin sensitivity) consti tute a major determinant in the variation in whole-body insulin sensitivity . Copyright (C) 2001 by W.B. Saunders Company.