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.

We followed the effects of sera from unilaterally nephrectomized (uninephectomized) rats compared to sham-operated rats on ³Η-p-aminohippurate (³H-PAH) and ¹⁴C-tetraethylammonium (¹⁴C-TEA) uptake and oxygen comsumption (QO₂) in incubating rat kidney slices. These studies were based on the assumption that a circulating renotropic substance might also influence various transport mechanisms. Sera were obtained at various times postoperation; the height of renotropic activity occurs 17–24 h after kidney extirpation. Sera removed 17–24 h postuninephrectomy significantly decreased both ³H-PAH and ¹⁴C-TEA uptake in incubating kidney slices. Similar to the inability to show significant renotropic activity after 36 h, sera obtained 48,96, and 168 h postuninephrectomy had no significant influence on ³H-PAH and ¹⁴C-TEA uptake. Addition of sera (10% v/v) generally depressed QO₂. However, sera obtained from uninephrectomized rats compared to sera from sham-operated rats had relatively more depressive effects on QO₂ in renal tissue after 30 min of incubation (p < 0.01). No significant differences in QO₂ were seen when the uninephrectomized and sham-operated sera were added to the tissue immediately or after 60 min of incubation in the sera. These serum studies on ³H-PAH and ¹⁴C-TEA uptake simulate in many respects ones performed previously with serum from spontaneously hypertensive and salt-loaded rats and suggest the presence of a common circulating factor.

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.

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