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 function al renal mass, we studied the blood pressure response to chronic infus ion of Ang II at a subpressor dose in partially nephrectomized rats. M ale Sprague-Dawley rats were subjected to 1/6, 2/6, 3/6, 4/6 and 5/6 n ephrectomy, and sham operation a week before the infusion of Ang II at a rate of 400 mug/kg/day delivered intraperitoneally by osmotic minip umps 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 n ot induce a significant change in systolic blood pressure in sham-oper ated 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 Il infusion among groups in 2/6, 3/6, 4/6 and 5/6 nephrectomized r ats. Blood urea nitrogen and serum creatinine levels, endogenous creat inine clearance, urinary excretion of protein as indices of renal func tion, and urinary sodium excretion were not affected by chronic infusi on of Ang II in 1/6, 2/6, 3/6, 4/6 and 5/6 nephrectomized, and sham-op erated rats. There was also no significant difference in circulating l evels of Ang II among Ang II infused-groups in 1/6 and 2/6 nephrectomi zed rats. These results indicate that elevated levels of circulating A ng II are capable of causing a sustained hypertension in rats with red uced functional renal mass. In addition, they also suggest that circul ating levels of Ang II could play a more important role in the regulat ion of blood pressure in rats with incipient impairments of renal func tion.