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(Hypertension. 1999;34:964-968.)
© 1999 American Heart Association, Inc.

Scientific Contributions

Cardiovascular Effects of Angiotensin-(1–7) in Conscious Spontaneously Hypertensive Rats

Robert E. Widdop; Donella B. Sampey; Bevyn Jarrott

From the Department of Pharmacology, Monash University, Clayton, Victoria, Australia.

Correspondence to Dr Robert Widdop, Department of Pharmacology, Monash University, Clayton, Victoria 3168, Australia. E-mail robert.widdop{at}med.monash.edu.au

Abstract—In the present study, we reassessed whether angiotensin (Ang)-(1–7) can exert short- and long-term cardiovascular effects because there has been a resurgence of interest in this N-terminal heptapeptide fragment of Ang II. In particular, we studied 3 aspects relating to the reported cardiovascular effects of Ang-(1–7): does this peptide (1) potentiate the hypotensive effect of bradykinin in normotensive Wistar-Kyoto rats and spontaneously hypertensive rats (SHR), (2) cause a depressor effect after long-term treatment in SHR, and (3) contribute to the antihypertensive effects of angiotensin-converting enzyme inhibitors? In the first series of experiments, Ang-(1–7) failed to enhance the dose-related hypotensive responses evoked by bradykinin in SHR (n=11) and Wistar-Kyoto (n=5) rats. In the second series of experiments, a 7-day intravenous infusion of Ang-(1–7) (24 µg · kg^-1 · h^-1) decreased blood pressure in SHR (n=12) on days 4 and 5, although this effect waned despite continual Ang-(1–7) infusion. However, a new finding was that the Ang-(1–7) antagonist A-779 (24 µg · kg^-1 · h^-1 for 7 days) attenuated the depressor effect of Ang-(1–7) when given concurrently in a separate group of SHR (n=8). In the third series of novel experiments, the angiotensin-converting enzyme inhibitor perindopril was given in drinking water for 7 days (0.3 mg · kg^-1 · day^-1), either alone (n=6) or combined with an intravenous infusion of A-779 (24 µg · kg^-1 · h^-1 for 7 days, n=8). Although this dose of A-779 attenuated the depressor effect of Ang-(1–7), it did not alter the antihypertensive effect caused by perindopril. Thus, the present results contrast with a number of previous studies and argue against Ang-(1–7) playing a major role in blood pressure regulation.

Key Words: angiotensin • bradykinin • angiotensin-converting enzyme inhibitors • rats, inbred SHR • blood pressure

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