Nonobese, hereditary hypertriglyceridemic (HTG) rats provide an interesting model of hypertriglyceridemia, glucose intolerance, and hypertension. In age-matched 15 HTG and 16 control Wistar rats fed on a high sucrose diet (70 cal%) for 6 weeks, we measured insulin sensitivity in vivo and some parameters of sympatoadrenal system. Using euglycemic clamps with administration of 2-deoxy1-3Hglucose, we found whole body insulin resistance and decreased glucose metabolic index Rg' in soleus muscle, epitrochlearis muscle, diaphragm, and white adipose tissue in HTG rats. We found higher levels of plasma epinephrine and higher excretion of vanilmandelic and homovanilic acids in HTG rats. The binding of 3H-dihydroalprenol to the heart membrane fraction was similar in both groups, but the dissociation constant Kd was increased by 75% in the heart of HTG rats.