Bradykinin antagonism and prostaglandins in blood pressure regulation.

These experiments were designed to analyze the interaction of a bradykinin antagonist with prostaglandins in blood pressure regulation of normotensive rats. Male Wistar rats, divided into three groups, received a 5-minute intra-arterial infusion of the bradykinin antagonist [( DArgo-Hyp3-Thi5,8-DPhe7]BK-TFA) at 250 micrograms/min. Groups were either intact rats (group I, n = 5), pretreated with indomethacin (group II, n = 10), or pretreated with both indomethacin and prazosin (group III, n = 8). The bradykinin antagonist infusion, which was shown to inhibit exogenous bradykinin by greater than 76% in intact animals, did not alter mean arterial pressure in group I rats despite a twofold increase in norepinephrine and a threefold increase in epinephrine. Group II rats presented a progressive increase in mean arterial pressure during the bradykinin antagonist infusion (14 +/- 3 mm Hg), with no statistically significant change in plasma catecholamines. Group III, with lower baseline mean arterial pressure due to alpha 1-adrenergic blockade, had an increase in mean arterial pressure comparable with group II during bradykinin antagonist infusion (22 +/- 5 mm Hg), confirming that this response was not sympathetically mediated. We conclude that in normotensive rats bradykinin plays a role in blood pressure regulation that is closely linked to that of prostaglandins and that points to a balance between these systems.