Arterial pressure and its regulation in rats bred successively on low sodium diet

To investigate the effects of long-term sodium restriction on mechanisms regulating cardiovascular function, Wistar rats at weaning (F0) were placed on a normal (0.4%) or low (0.05%) sodium diet. The first (F1) and second (F2) generations were derived from inbreeding within each group. The resting mean arterial pressure did not differ between the diet groups of F0 or F1 rats, but it was significantly lower in F2 rats on the low sodium diet. Plasma renin concentration was similar in the two groups in each generation, and the F2 rats on both diets responded to [Sar1, Ala8] angiotensin II with the same degree of decrease in arterial pressure. Plasma norepinephrine was not influenced by sodium intake in the F0 or F1 rats, but was significantly lower in F2 rats on the low sodium diet. The depressor response to hexamethonium was similar in the two F1 groups, while low sodium F2 rats exhibited a lesser response. These results suggest that rats bred successively on a low sodium diet have a suppressed sympathetic nerve function with no enhancement of the renin-angiotensin system, which in turn results in a lower arterial pressure.