We have reported that chronic insulin infusion increases mean arterial pressure (MAP) in rats. In those studies, glucose was coinfused to prevent hypoglycemia, but it is possible that the glucose infusion rate may have exceeded the rate actually required to prevent hypoglycemia. If true, then the glucose infusion alone should have a similar effect, and this study tested that hypothesis. In six rats (insulin group) instrumented with artery and vein catheters, insulin was infused for 7 days intravenously (iv) at 1.5 mU/kg/min together with glucose iv at 18.6 mg/kg/min. Seven other rats (glucose group) received the same glucose infusion for 7 days but without iv insulin. MAP increased significantly in both groups, from 98 +/- 3 and 96 +/- 2 mm Hg to 107 +/- 5 and 104 +/- 3 mm Hg in the insulin and glucose groups, respectively, and the renal and hormonal changes were similar to those previously reported during insulin infusion. There were no significant differences between the two groups for any variable measured. These data indicate that the sugar intake provided by the glucose infusion essentially mimics the response to our insulin and glucose infusion protocol, and that similar mechanisms underlie the renal and cardiovascular responses to each protocol.