The augmented blood pressure response to chronic angiotensin II infusion in partially nephrectomized rats

To assess potential roles of circulating levels of angiotensin II (Ang II) in the regulation of blood pressure in rats with reduced functional renal mass, we studied the blood pressure response to chronic infusion of Ang II at a subpressor dose in partially nephrectomized rats. Male Sprague-Dawley rats were subjected to 1/6, 2/6, 3/6, 4/6 and 5/6 nephrectomy, and sham operation a week before the infusion of Ang II at a rate of 400 micrograms/kg/day delivered intraperitoneally by osmotic minipumps for 14 days, or vehicle alone served as controls. Infusion of Ang II was associated with a slight but significant increase in systolic blood pressure in 1/6 nephrectomized rats (p < 0.05), whereas it did not induce a significant change in systolic blood pressure in sham-operated rats. Hypertension during Ang II infusion was more prominent in 2/6 nephrectomized rats than that in 1/6 nephrectomized rats (p < 0.05). However, there was no significant difference in hypertension during Ang II infusion among groups in 2/6, 3/6, 4/6 and 5/6 nephrectomized rats. Blood urea nitrogen and serum creatinine levels, endogenous creatinine clearance, urinary excretion of protein as indices of renal function, and urinary sodium excretion were not affected by chronic infusion of Ang II in 1/6, 2/6, 3/6, 4/6 and 5/6 nephrectomized, and sham-operated rats. There was also no significant difference in circulating levels of Ang II among Ang II infused-groups in 1/6 and 2/6 nephrectomized rats. These results indicate that elevated levels of circulating Ang II are capable of causing a sustained hypertension in rats with reduced functional renal mass.(ABSTRACT TRUNCATED AT 250 WORDS)