title: Angiotensin-(1-7) potentiates the hypotensive effect of bradykinin in conscious rats.
abstract: Treatment with angiotensin-converting enzyme inhibitors increases the angiotensin-(1-7) [Ang-(1-7)] and bradykinin concentrations in plasma and tissue. In this study we evaluated the interaction between these peptides by determining the effect of Ang-(1-7) on the hypotensive action of bradykinin in conscious rats. Administration of Ang-(1-7) (5 nmol) did not change mean arterial pressure or heart rate. However, the hypotensive effect of bradykinin, produced by an intravenous or intra-arterial route, was potentiated by Ang-(1-7) in a dose-dependent manner. The Ang-(1-7) doses necessary to transform the effect of a single dose of bradykinin into that produced by a double dose (potentiating unit) were 2 nmol i.v. and 5 nmol IA. The Ang-(1-7) dose used did not change either the pressor effect of Ang II or the hypotensive effect of sodium nitroprusside. The bradykinin-potentiating Ang-(1-7) activity was significantly attenuated by pretreatment with indomethacin (5 mg/kg IM, n = 4). In an additional group the bradykinin-potentiating activity of Ang-(1-7) was evaluated 30 minutes after treatment with the angiotensin-converting enzyme inhibitor enalaprilat (10 mg/kg i.v., n = 9). Under this condition the bradykinin-potentiating activity of Ang-(1-7) was substantially increased, resulting in a potentiating unit of approximately 0.2 nmol IV. Pretreatment with indomethacin (5 mg/kg IM, n = 7) also attenuated the bradykinin-potentiating activity of Ang-(1-7) in enalaprilat-treated rats. These results show that Ang-(1-7) is a bradykinin-potentiating peptide in vivo. Furthermore, the data obtained with indomethacin suggest that prostaglandins participate in the mechanism of the bradykinin potentiation by Ang-(1-7). More importantly, these data suggest that the interaction between Ang-(1-7) and bradykinin can contribute to the pharmacological effects of angiotensin-converting enzyme inhibitors.
mesh_terms: D000803:Angiotensin I; D000804:Angiotensin II / Q000008:administration & dosage / Q000494:pharmacology*; D000806:Angiotensin-Converting Enzyme Inhibitors / Q000494:pharmacology; D000818:Animals; D000894:Anti-Inflammatory Agents, Non-Steroidal / Q000494:pharmacology; D000959:Antihypertensive Agents / Q000494:pharmacology; D001794:Blood Pressure / Q000187:drug effects* / Q000502:physiology; D001920:Bradykinin / Q000008:administration & dosage / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004357:Drug Synergism; D015773:Enalaprilat / Q000494:pharmacology; D007213:Indomethacin / Q000494:pharmacology; D008297:Male; D010446:Peptide Fragments / Q000008:administration & dosage / Q000494:pharmacology*; D011453:Prostaglandins / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D012084:Renin-Angiotensin System / Q000502:physiology; D014662:Vasoconstrictor Agents / Q000008:administration & dosage / Q000494:pharmacology*
chemical_list: D000806:Angiotensin-Converting Enzyme Inhibitors; D000894:Anti-Inflammatory Agents, Non-Steroidal; D000959:Antihypertensive Agents; D010446:Peptide Fragments; D011453:Prostaglandins; D014662:Vasoconstrictor Agents; D000804:Angiotensin II; D000803:Angiotensin I; D015773:Enalaprilat; C118790:angiotensin I (1-7); D001920:Bradykinin; D007213:Indomethacin