Regulatory role of bradykinin in the coronary and cerebral circulations and in systemic hemodynamics

Bradykinin (BK) increased carotid blood flow (CBF) and jugular nitric oxide (NO) levels when administered into the common carotid artery of rabbits, a nd potentiated selectively, when infused together with histamine (HIST) or serotonin (5-HT), their effects on both CBF and jugular NO levels (but not vice versa). Such a potentiation was prevented and reversed only by nitroar ginine or 1,10-phenanthroline (PHE) (which also reduced basal jugular NO le vels) and did not involve the BK, or BK, receptors. Either HIST or 5-HT pot entiated (likely involving the H-1 and 5-HT2 receptors, respectively) the a ctivating effect of BK on kininase I (K1), thus increasing the availability of L-arginine for the synthesis of NO. In patients with migraine, venous N O and K1 activity were higher during KIST desensitization than in basal con ditions; moreover, KIST reduced the activities of prekallikrein (pre-KAL), kallikrein (KAL) and kininase II (K2) in the venous blood of these patients , in which the intensity of pain was related to the levels of plasma NO, an d the administration into the humeral artery during circulatory arrest of B K alone (but not KIST) or BK and KIST together caused a strong pain attack. BK was confirmed to interact selectively with other autacoids in regulatin g systemic and local hemodynamics through the system of NO. (C) 1999 Elsevi er Science B.V. All rights reserved.