Presser and renal effects of intracerebroventricularly administered angiotensins II and III in rats

Aims: Experiments were performed to assess the effects of intracerebroventr icular (ICV) angiotensin (ANG) III on blood pressure and renal function in rats with normal and high sodium intake and to compare these effects with t hose produced by ICV ANG II. Methods: Male Sprague-Dawley rats on a normal sodium (0.3%) diet and a normal sodium diet plus 1% NaCl as drinking water were administered ANG II and ANG III ICV through a chronically implanted ca nnula. Blood pressure and renal clearance function responses were measured before and during peptide administrations. The effect of ICV ANG III on the renal efferent nerve activity was also evaluated. Results: ICV injections of ANG II and ANG III at 5 pmol in rats on a normal sodium diet did not sig nificantly alter the blood pressure, but significantly increased renal plas ma flow glomerular filtration rate, urine flow, and absolute and fractional excretions of sodium and potassium. Increased doses of ANG II and III (10, 50 and 100 pmol) significantly increased blood pressure and further enhanc ed these renal functional indices. Central ANG-III-induced increases in blo od pressure and renal functional indices were not significantly different f rom those produced by ANG II at each corresponding dose. The presser and re nal effects of ANG III were blunted by a specific antagonist, lle(7)-ANG II I. ICV administration of ANG III decreased the renal efferent nerve activit y. In rats with dietary NaCl loading, ICV injections of ANG II and III also significantly enhanced renal function. Conclusions: Centrally administered ANG III is as potent as ANG II in causing presser and renal effects in rat s on normal and high sodium intake. As ANG II, brain ANG III reduced renal efferent nerve activity whrich may be partly accounted for the augmented re nal function. Copyright (C) 2000 S. Karger AG, Basel.