High dietary sucrose can chronically increase SBP in three substrains of Wistar rats. Increased concentrations of circulating insulin were found in WKY and WAM suggesting that the glucose/insulin system was involved, at least in these two substrains, in the maintenance of high SBP levels during chronic, heavy sugar ingestion.

Spontaneously hypertensive rats (SHR) were fed 6 different diets. The baseline diet (I) derived equal calories from sucrose, proteins, and fats. Three other diets (II, III, VI) derived the majority of calories from refined CHO, sucrose or glucose, with decreases in calories from proteins or fats. The last two diets (IV, V) were relatively low in sucrose with a higher percentage of the total calories from proteins and fats, respectively. From 3 to 15 weeks on the diets, the highest average BP was in rats consuming high concentrations of sucrose or glucose (II, III, VI). Urinary excretory rates of norepinephrine (NE) at 5, 10 and 15 weeks and epinephrine at 5 and 10 weeks were significantly elevated in rats ingesting diets high in refined CHO, and NE positively correlated with blood pressure (BP) at 5 and 10 weeks of the study. At the end of the study, serum insulin levels were not different, but plasma renin and serum glucagon levels were lower in SHR consuming the diets with high CHO concentrations. We conclude that equally elevated BP are seen with relatively high intakes of either sucrose or glucose, whether the balance of calories is derived from lessening fat or protein. This is secondary, at least in part, to alterations in NE metabolism.

Among four strains examined, spontaneously hypertensive rats (SHR) show a marked (20 mm Hg, P less than .01) systolic blood pressure elevation (SBP), Sprague-Dawley (SD) and Wistar-Kyoto (WKY) rats developed a moderate elevation (8 mm Hg, P less than .01), and a normotensive Wistar rat (WAM) had a lesser SBP elevation (6 mm Hg, P = NS) after excess sucrose ingestion. The SBP elevations found in SHR were noted at 2 and 4 weeks after starting the dietary treatments. Corresponding with SBP changes, plasma renin activity (PRA), aldosterone, and neuropeptide Y (NPY) concentrations all decreased with the high sucrose-low protein diet compared to the low sucrose-high protein diet, while circulating insulin levels were unchanged. Although norepinephrine (NE) and epinephrine (E) excretion tended to be higher in the rats eating the high sucrose-low protein food, the differences were not statistically significant. The differences in these parameters could influence the SBP in SHR, SD, and WKY, but virtually similar qualitative and quantitative blood and urinary findings were found in WAM, a strain of rat that showed no significantly increased SBP. Removing one kidney increases the CHO-induced SBP response of WKY to levels comparable to those seen in SHR, converting a moderate responder to a highly sensitive one. We conclude that under well-controlled conditions there are obvious differences in the SBP response to the macronutrients in the diets of various rat strains and that SHR possess some intrinsic mechanism(s), most likely associated with renal metabolism, which make this strain more sensitive to refine CHO-induced SBP elevations.

SummaryIt is generally accepted that ingestion of sucrose in large quantities elevates blood pressure (BP). Less certain is whether starch and other refined carbohydrates (CHO) have similar effects. Using spontaneously hypertensive rats (SHR) and normotensive control rats (WKY), we show that glucose, fructose, and starch fed to rats either in solution or in dry form elevate BP to a similar degree as sucrose. The changes in BP brought on by various refined CHO were greater in SHR than in WKY. The elevations did not consistently correlate with differences in body weight, amount of dry matter or fluid intake, the quantities of sodium and potassium ingested, or to changes in the various blood chemistries examined. We conclude that other refined CHO (glucose, fructose, and starch) like sucrose raise BP significantly. This effect on BP is rapid (within days) and reversible, at least to some extent.Key Words: carbohydrates, effects on blood pressure, spontaneously hypertensive rats, effect of CHO, macronutrients Excess ingestion of sucrose, a disaccharide of glucose and fructose, elevates blood pressure (BP) in rats [1]. However, it is uncertain whether simple carbohydrates (CHO) other than sucrose cause similar BP increases. Because previous studies have been inconsistent, glucose, fructose, and starch individually cannot be conclusively implicated in a BP response. For example, Hall and Hall [2] found that addition of glucose to a saline drinking solution elevates BP but was significantly less hypertensive than the combination of sucrose plus saline. Honey, which is composed of fructose, did not elevate BP when added to saline. Beebe

We placed groups of spontaneously hypertensive rats (SHR), Wistar-Kyoto rats (WKY) and a local strain of normotensive Wistar rats on 5 different diets. Our baseline diet (I) derived a near equal number of calories from sucrose, proteins and fats, ie, 1/3 of total calories was provided by each macronutrient. Two other diets (II,III) derived the majority of calories from sucrose with less calories from proteins or fats respectively. The last two diets (IV,V) were relatively low in sucrose with a higher percentage of the total calories from proteins or fats respectively. The rats were assigned to the special diets at 3 months of age. They have now been ingesting these diets a total of 12 months. In SHR, the diets highest in sucrose calories (II,III), in contrast to diets I,IV and V, were associated with a markedly increased blood pressure (BP) at 3 months. The difference of approximately 20 to 30 mm Hg has held over 12 months. In contrast, the normotensive Wistar rats consuming diets II and III showed significant differences in BP (approximately 10 mm Hg) only after 12 months. The response of WKY was intermediate. Some clearcut elevation of BP, although not statistically significant, in WKY consuming diets II and III was present by 3 months. This difference became greater with time (20 mm Hg at 12 months). Consistent changes in body weights between the rats on the different diets were lacking. We conclude that excess ingestion of sucrose can cause chronic elevations in BP, the pattern of which varies among rat strains.