HIGH-FRUCTOSE DIET DOES NOT RAISE 24-HOUR MEAN ARTERIAL-PRESSURE IN RATS

High intakes of the simple sugars-glucose, sucrose, and fructose-have been reported to raise significantly systolic pressure in rats. It is not clear, however, if under those conditions the acute measurement of blood pressure, especially with the tail-cuff technique, represents accurately the effect of the diet on mean arterial pressure throughout the day. In this study, 15 Sprague-Dawley rats (approximately 325 g) were chronically instrumented with arterial and venous catheters and placed on a diet containing 61% vegetable starch and 5% dextrose; seven rats remained on this diet throughout the study. After 4 days of control measurements, eight rats were switched to a diet that substituted 66% fructose for the vegetable starch and dextrose. Mean arterial pressure (MAP) was measured 20 h/day by computerized methods. MAP during the 4 control days averaged 100 +/- 3 and 105 +/- 3 mm Hg in low-fructose (LF) and high-fructose (HF) diet rats, respectively. Switching to the HF diet caused no change in MAP, and after 11 days MAP averaged 104 +/- 2 and 108 +/- 3 mm Hg in the LF and HF rats, respectively. In addition, the variability of MAP over the 20-h period each day was not altered by the HF diet, and raising sodium intake fourfold caused a similar rise in MAP in both groups. There also were no significant changes in plasma glucose or insulin concentrations. Thus, a change in dietary simple sugar content from 5% dextrose to 66% fructose did not change MAP or alter blood pressure variability or sodium sensitivity. This suggests that acute blood pressure measurement under these conditions may not reflect accurately the hemodynamic response to high-sugar diets. However, the potential for other factors, such as rat strain, to explain the different responses to high-sugar diets should be explored further, and the long-term effect of these diets on blood pressure, perhaps mediated through changes in lipid metabolism, remains unknown.