Ca2+ signalling of kinins in cells expressing rat, mouse and human B1/B2-receptor.

With respect to functional aspects, the kallikrein-kinin-system can be divided into a plasma kallikrein-kinin-system and a tissue kallikrein-kinin-system. At least four functional kinin peptides act via two different G-protein-coupled receptors, an inducible B1-receptor and a constitutively expressed B2-receptor. B1R and B2R couple to G(q/11) and lead via phospholipase C to Ca2+ mobilization. In humans both, bradykinin and kallidin are agonists on the B2-receptor. In contrast, bradykinin is believed to be the only kinin acting on the B2R in rats and mice. However, recently we have isolated a kallidin-like-peptide from plasma and urine of rats. Until now the kinin ligand-receptor interactions were mainly characterized in binding studies. However, receptor affinity does not inevitably correspond with the intrinsic activity of an agonist. The aim of the present study was to investigate intracellular calcium mobilization to quantify mouse, rat and human B1- and B2-receptor activation by bradykinin, kallidin, des-Arg9-bradykinin, des-Arg10-kallidin, and of the two novel rat kinins, kallidin-like-peptide and des-Arg10-kallidin-like-peptide. In cells stably expressing the human, rat, and mouse B2-receptor, respectively, bradykinin, kallidin, and kallidin-like-peptide were nearly equipotent (EC50, 10(-12)M) at eliciting Ca2+-transients. Their des-Arg-derivatives were 10(3)-fold less potent. In cells expressing B1-receptor the des-Arg derivatives elicited Ca2+-signals at an EC50 in the order of 10(-9)M. Major differences between these peptides could not be observed. Bradykinin, kallidin, and kallidin-like-peptide caused a Ca2+-signal at substantially higher concentrations in the order of 10(-7)M. The data show that des-Arg9-bradykinin, des-Arg10-kallidin, and des-Arg10-kallidin-like-peptide are equipotent agonists at the B1-receptor. Bradykinin, kallidin and kallidin-like-peptide are equipotent agonists at the B2-receptor.

Kallidin-like peptide mediates the cardioprotective effect of the ACE inhibitor captopril against ischaemic reperfusion injury of rat heart.

1. The potential cardioprotective effect of ACE inhibitors has been attributed to the inhibition of bradykinin degradation. Recent data in rats documented a kallidin-like peptide, which mimics the cardioprotective effect of ischaemic preconditioning. This study investigates in isolated Langendorff rat heart the effect of the ACE inhibitor captopril, the role of bradykinin, kallidin-like peptide, and nitric oxide (NO). 2. The bradykinin level in the effluent of the control group was 14.6 pg ml(-1) and was not affected by captopril in the presence or absence of kinin B2-receptor antagonist, HOE140. 3. The kallidin-like peptide levels were approximately six-fold higher (89.8 pg ml(-1)) and increased significantly by treatment with captopril (144 pg ml(-1)), and simultaneous treatment with captopril and HOE140 (197 pg ml(-1)). 4. Following 30 min ischaemia in the control group, the creatine kinase activity increased from 0.4 to 53.4 U l(-1). In the captopril group and in the captopril+L-NAME group, the creatine kinase activity was significantly lower (18.5 and 22.8 U l(-1)). This beneficial effect of captopril was completely abolished by the kinin B2-receptor antagonist, HOE140, as well as by the kallidin antiserum. 5. Perfusion of the hearts with kallidin before the 30 min ischaemia, but not with bradykinin, yielded an approximately 50% reduction in creatine kinase activity after reperfusion. 6. Pretreatment with L-NAME alone and simultaneously with captopril, and with kallidin, respectively, suggests a kinin-independent action of NO before the 30 min ischaemia on coronary flow and a kinin-dependent action after ischaemia. 7. These data show that captopril increases kallidin-like peptide in the effluent. Kallidin-like peptide via kinin B2 receptor seems to be the physiological mediator of cardioprotective actions of captopril against ischaemic reperfusion injury. HOE140 as well as the kallidin antiserum abolished the cardioprotective effects of captopril.

A kallidin-like peptide is a protective cardiac kinin, released by ischaemic preconditioning of rat heart.

Bradykinin is thought to play a major role among the endogenous cardioprotective candidates of ischaemic preconditioning (IPC). Little attention has been paid to the fact that in the tissue kallidin (KAL), rather than bradykinin might be the physiological mediator of the kallikrein-kinin system. In order to evaluate the importance of one or the other peptide the release and effect of both kinins has been investigated in isolated rat hearts following IPC. Bradykinin- and a KAL-like peptide were measured in the effluent of the rat isolated Langendorff heart with two different specific radioimmunoassays. The creatine kinase activity in the effluent was judged as degree of cardiac injury caused by ischaemia. During IPC, which consists of three 5 min no-flow and 5 min reperfusion cycles prior to the 30 min ischaemia, the bradykinin level in the effluent did not change significantly (15.4-19.4 pg ml(-1)). In the control group the bradykinin levels were 15.9-16.6 pg ml(-1). During IPC KAL-like peptide (Arg(1)-, instead of Lys(1)-KAL), which has recently been verified by mass spectrometry, displays 5.8-fold higher levels in the effluent and significantly increases in the same time interval from 90.4 to 189 pg ml(-1). After 30 min ischaemia the bradykinin levels in the IPC group were not significantly different to those of the control group (18.7 vs 14.4 pg ml(-1)). The KAL-like peptide levels in the IPC group vs the control group were 105 vs 86.1 pg ml(-1). By the 30 min ischaemia the creatine kinase activity in the IPC group increased from 0.367 to 8.93 U l(-1) (before and 10-30 min after ischaemia). In the control group during the same time period the creatine kinase levels increased from 0.277 to 34.9 U l(-1). The low increase in creatine kinase activity following IPC was taken as equivalent of the cardioprotective action. A KAL antibody or HOE140 (kinin B(2)-receptor antagonist) completely abolished this beneficial effect of IPC (36.6 and 53.0 U l(-1)) when added to the perfusion medium during the reperfusion cycles of IPC prior to the 30 min ischaemia. Our data suggest that in rat hearts KAL-like peptide rather than bradykinin is the physiological compound activated by IPC and acting via the cardiac kinin B(2)-receptor. Thus, endogenously generated KAL-like peptide seems to play a major role in the cardioprotection of IPC.