Sodium balance and hypertension in obese and fatty rats.

To investigate the role of sodium in obesity induced hypertension, Wistar fatty rats (WFR) were employed. This rat has the following characteristics: (1) hyperglycemia, (2) hyperinsulinemia, and (3) hypertriglycemia. Four percent sodium chloride with constant amount of food intake was administered to these rats from 8 to 16 weeks. During this period, body wt, food intake, water consumption, urine volume, systolic blood pressure, urinary excretion of sodium and potassium, urinary albumin excretion, plasma sodium and potassium, and plasma glucose and immunoreactive insulin (IRI) were measured before, and twice more during eight weeks. No remarkable changes were observed in plasma glucose level during these periods between the two groups. On the other hand, in group 1 IRI significantly increased compared with group 2. Mean blood pressure was increased from 110 +/- 5 to 130 +/- 8 mm Hg (P < 0.01). To ascertain whether this salt sensitivity relates to the abnormalities in pressure-natriuresis responses, the pressure-natriuresis (P-N) was characterized. The P-N curve in WFR was shifted to the right and its slope was flattened compared to its control Wistar lean rats. In conclusion, an excess of dietary sodium intake may contribute to an elevation of blood pressure in Wistar fatty rat with hyperglycemia and hyperinsulinemia. This salt sensitivity may change the abnormal pressure-natriuresis responses.