Contribution of bradykinin to maintenance of normal blood pressure

The purpose of these experiments was to investigate whether the vasodilator tissue hormone bradykinin contributes to the maintenance of normal blood pressure. A newly synthesized peptide competitive antagonist of bradykinin, the compound Arg-Pro-Hyp-Gly-Phe-Ser-DPhe-Phe-Arg-trifluoracetic acid (B3852), capable of inhibiting the depressor effect of exogenous bradykinin by over 50%, was infused into 10 normotensive rats at a rate of 500 micrograms/0.1 ml/min. Blood pressure rose immediately, from a baseline of 104 +/- 5 to 131 +/- 7 mm Hg at the end of a 5-minute infusion, and returned to baseline within 2 to 3 minutes after discontinuation of the infusion. When similar doses were administered by continuous infusion to previously nephrectomized rats (n = 5) or as an acute bolus to adrenalectomized rats (n = 5), blood pressure rose from 111 +/- 3 to 125 +/- 5 mm Hg and from 112 +/- 4 to 128 +/- 5 mm Hg, respectively. The data suggest that a vasodepressor action of endogenous bradykinin contributes to maintenance of normal peripheral vascular tone, and that this action is not mediated through adrenal catecholamines or renomedullary prostaglandins.