Kinin-induced prolongation of action-potential duration in right ventricular muscle from rat: involvement of B1 and B2 receptors

Bradykinin induced sustained anti-adrenergic actions in guinea pig heart muscle involves PKC

OBJECTIVES

Adenosine attenuates the effect of beta-adrenergic stimulation upon contractile force, both when present during beta-adrenergic stimulation and for a period after washout of adenosine. Protein kinase C (PKC) mediates the sustained effect. The present study investigated if bradykinin (500 nM) could induce anti-beta-adrenergic actions.

DESIGN

Guinea pig papillary muscles (36.5 degrees C, 1 Hz) were subjected to 15 min exposure to and 20 min washout of bradykinin. Isoproterenol 100 nM was added for 3 min at the end of test exposure and at the end of washout. The PKC-inhibitor bisindolylmaleimide (20 nM) was given to investigate the importance of PKC.

RESULTS

Bradykinin significantly reduced the increase in contractile force in response to isoproterenol, both when present and after washout of test substance. Inhibition of PKC abolished the sustained effect, while inhibition of PI3-kinase with wortmannin did not seem to affect the results.

CONCLUSIONS

Anti-beta-adrenergic effects of bradykinin on contractile force and action potential duration were demonstrated. PKC was important for the sustained effect on contractile force, but not for the acute effect and the effect on action potential duration.

Participation of kallikrein-kinin system in different pathologies

The general description of kinins refers to these peptides as molecules involved in vascular tone regulation and inflammation. Nevertheless, in the last years a series of evidences has shown that local hormonal systems, such as the kallikrein-kinin system, may be differently regulated and are of pivotal importance to pathophysiological control. The combined interpretations of many recent studies allow us to conclude that the kallikrein-kinin system plays broader and richer roles than those classically described until recently. In this review, we report findings concerning the participation of the kallikrein-kinin system in inflammation, cancer, and in pathologies related to cardiovascular, renal and central nervous systems.

Detection of bradykinin B1 receptors in rat aortic smooth muscle cells

The tritiated bradykinin B1 receptor agonist [3H]des-Arg(10)-kallidin bound to a single class of high-affinity binding sites (K(d) = 0.5 +/- 0.16 nM; B(max) = 15,000 +/- 8,000 sites/cell) on cultured rat aortic smooth muscle cells. [3H]Des-Arg(10)-kallidin association and dissociation kinetics were monoexponential, making it possible to determine the association and dissociation rate constants (k(+1) = 1.5 10(5) M(-1) sec(-1); k(-1) = 4.2 10(-5) sec(-1)). [3H]Des-Arg(10)-kallidin binding was inhibited by specific ligands of bradykinin B1 and B2 receptors with a rank order of potency consistent with that known for bradykinin B1 receptors in other species (des-Arg(9)-[Leu(8)]bradykinin = des-Arg(10)-kallidin = des-Arg(9)-bradykinin = des-Arg(10)-[Leu(9)]kallidin > des-Arg(10)-HOE-140 >> bradykinin >> HOE-140). Bradykinin B1 receptor mRNA was also detected in these cells. Des-Arg(10)-kallidin increased cytosolic free Ca2+ levels, phosphoinositide turnover, and arachidonic acid release at nanomolar concentrations (respective EC(50) values: 16 +/- 2, 4 +/- 2.7, 6 +/- 2 nM). These functional effects of des-Arg(10)-kallidin could be blocked by the bradykinin B1 receptor antagonist des-Arg(9)-[Leu(8)]bradykinin, but were not sensitive to bradykinin B2 receptor antagonists. These results therefore show that rat aortic smooth muscle cells in culture express functional bradykinin B1 receptors.