Mediation by B1 and B2 receptors of vasodepressor responses to intravenously administered kinins in anaesthetized dogs.
1. Vasodepressor responses to intravenous (i.v.) injection of bradykinin (BK) and des-Arg9-BK, a selective B1 kinin receptor agonist, were characterized following i.v. pretreatment with selective B1 ([Leu8]-des-Arg9-BK) and B2 (Hoe 140) kinin receptor antagonists in anaesthetized dogs. 2. Des-Arg9-BK (0.05-3.3 nmol kg-1) produced dose-dependent decreases in mean arterial blood pressure with a ED50 0.4 nmol kg-1. The vasodepressor effects evoked by des-Arg9-BK (0.6 nmol kg-1) and BK (0.2 nmol kg-1) were greater after i.v. and i.a. injections, respectively. 3. The vasodepressor response to BK (0.6 nmol kg-1) but not to des-Arg9-BK (0.6 nmol kg-1) was significantly (P < 0.001) blocked by pretreatment with the B2 receptor antagonist, Hoe 140. 4. The vasodepressor response to des-Arg9-BK (0.6 nmol kg-1) but not to BK (0.6 nmol kg-1) was significantly (P < 0.001) reduced by pretreatment with the selective B1 receptor antagonist, [Leu8]-des-Arg9-BK. Although both B1 and B2 receptor antagonists caused a transient fall in blood pressure, their inhibitory action was unlikely to be related to a desensitization mechanism. 5. Inhibition of prostaglandin synthesis with indomethacin prevented the vasodepressor response induced by arachidonic acid (1 mg kg-1, i.v.) but not that to BK or des-Arg9-BK (0.6 nmol kg-1). 6. These results suggest, firstly, that the vasodepressor responses to i.v. BK and des-Arg9-BK are mediated by the activation of B2 and B1 receptors, respectively; secondly, that prostaglandins are not involved in the vasodepressor responses to kinins.These findings provide pharmacological evidence for the existence of functionally active B1 receptors in canine cardiovascular homeostasis.
Nakhostine
N
N
Department of Physiology, Faculty of Medicine, Université de Montréal, Québec, Canada.
Ribuot
C
C
Lamontagne
D
D
Nadeau
R
R
Couture
R
R
D000758:Anesthesia; D000818:Animals; D001772:Blood Cell Count; D001774:Blood Chemical Analysis; D001794:Blood Pressure / Q000187:drug effects*; D001920:Bradykinin / Q000031:analogs & derivatives / Q000494:pharmacology; D065168:Bradykinin Receptor Antagonists; D003864:Depression, Chemical; D004285:Dogs; D004305:Dose-Response Relationship, Drug; D005260:Female; D007213:Indomethacin / Q000494:pharmacology; D007275:Injections, Intravenous; D007705:Kinins / Q000008:administration & dosage / Q000494:pharmacology*; D008297:Male; D018002:Receptors, Bradykinin / Q000187:drug effects / Q000502:physiology*
D065168:Bradykinin Receptor Antagonists; D007705:Kinins; D018002:Receptors, Bradykinin; C024626:bradykinin, des-Arg(9)-; C065679:icatibant; D001920:Bradykinin; D007213:Indomethacin