Studies on the induction of pharmacological responses to des‐Arg⁹‐bradykinin in vitro and in vivo

Abstract

1The mechanisms by which agents modulate the induction ofkinin B,-receptors were investigated by studying the effects of kinins in vitro, by use of the rabbit isolated aorta, and in vivo by measuring the blood pressure of anaesthetized rabbits. 2 The contractile response ofthe rabbit isolated aorta to kinins increased in a time-dependent manner in vitro. This effect was abolished by continuous exposure to the protein synthesis inhibitor cycloheximide (71 gM).3 Several substances were found to increase specifically the rate of sensitization to des-Arg9-bradykinin (des-Arg9-Bk), when applied continuously in vitro to tissues isolated from normal animals: bacterial lipopolysaccharide (LPS; I ;Lg ml'), muramyl-dipeptide (MDP; 2 pg ml-'), phorbol myristate acetate (PMA; 320 nM), epidermal growth factor (EGF; 100 ng ml-') and endothelial cell growth factor (150 l~g ml-'). 5 It has been demonstrated that LPS induces B,-receptors in rabbits enabling des-Arg9-Bk to act as a hypotensive agent. In these experiments neutropenia induced by nitrogen mustard, did not prevent the in vivo effect of LPS. MDP (300 pg) and PMA (1I00 jg) were also found to induce a state of responsiveness to des-Arg9-Bk in vivo. FMLP (I mg i.v.) induced a temporary decrease in blood neutrophil counts but had no effect on the induction of responses to des-Arg9-Bk. 6 The development of responses mediated by the B,-receptor in the two experimental systems seems to be unrelated to the activation of neutrophil leukocytes, but may be related to the activation of tissue macrophages. Approximately 3% of cultured adherent cells derived from rabbit aorta strips following protease digestion were stained for non-specific esterase, supporting such a possibility.

Bradykinin B1 receptors in the rabbit urinary bladder: induction of responses, smooth muscle contraction, and phosphatidylinositol hydrolysis

“…In the presence of the carboxypeptidase inhibitor mergetpa, responses to bradykinin were still inhibited by [Leu8,des-Argl-BK (1-30JiM; n = 6; data not shown). Regoli et al, 1977), rabbit mesenteric artery (Regoli et al, 1978;Boutillier et al, 1987) and rat duodenum (Boschcov et al, 1984). Once stabilized, responses to [des-Argl-BK in both the rabbit bladder and aorta preparations were competitively antagonized by B1 receptor-selective antagonists.…”

Mediation by B1 and B2 receptors of vasodepressor responses to intravenously administered kinins in anaesthetized dogs

“…Despite the very well known B2 receptor-mediated vasodepressor effect of kinins (Regoli & Barabe, 1980;Bhoola et al, 1992), the cardiovascular activity of the natural kininase I metabolite, des-Arg9-BK, which is a selective B, receptor agonist, has been less studied. This fact is due in part to the belief that B, receptors are not expressed in normal tissues but are synthesized de novo during tissue incubation in vitro and as a result of inflammation or exposure of tissue to chemical noxious stimuli in vivo (Marceau et al, 1983;Bouthillier et al, 1987). For instance, des-Arg9-BK had no significant effect on the cardiovascular system of rats and rabbits whereas exogenous des-Arg9-BK lowered mean arterial blood pressure through the activation of peripheral vascular B, receptors in rabbits pre-injected intravenously 5 h earlier with a bacterial lipopolysaccharide Marceau et al, 1983;Bouthillier et al, 1987).…”

“…This fact is due in part to the belief that B, receptors are not expressed in normal tissues but are synthesized de novo during tissue incubation in vitro and as a result of inflammation or exposure of tissue to chemical noxious stimuli in vivo (Marceau et al, 1983;Bouthillier et al, 1987). For instance, des-Arg9-BK had no significant effect on the cardiovascular system of rats and rabbits whereas exogenous des-Arg9-BK lowered mean arterial blood pressure through the activation of peripheral vascular B, receptors in rabbits pre-injected intravenously 5 h earlier with a bacterial lipopolysaccharide Marceau et al, 1983;Bouthillier et al, 1987). Nevertheless, under normal conditions, both B, and B2 receptors appear to mediate the vasodilator action of kinins in the canine renal artery in vitro (Rhaleb et al, 1989) as well as the vasorelaxation responsible for an increased renal blood flow in the dog in vivo (Lortie et al, 1992).…”

Non‐competitive pharmacological antagonism at the rabbit B1 receptor

“…Thus, it was hypothesized that some of the residual e ects of desArg 9 -BK in the presence of a representative insurmountable antagonist, B-9858, may be partially dependent on the renewal of receptors at the cell surface. The use of protein synthesis inhibitors such as CHX supports the concept of tissue injury-induced de novo formation of B 1 receptors (Bouthillier et al, 1987;Audet et al, 1994). Notably, when CHX is applied from the beginning of the in vitro incubation, rabbit aortic tissues remain unresponsive to des-Arg 9 -BK, but respond to the agonists of other receptor types in a stable manner.…”

“…One of the six antagonists listed in Table 1, or the saline vehicle in control tissues, was introduced at time 5 h and maintained in the bathing¯uid during the construction of the second curve (e ect of the antagonist at 5.5 h). Contractility results were expressed as a per cent of the maximal response recorded in each tissue when constructing the control curve (3.5 h); this calculation accounts for the fact that the maximal response to this kinin increases as a function of the post-isolation incubation time in this preparation (a behaviour speci®c for agonists of B 1 receptors and attributed to the post-isolation formation of these receptors; Bouthillier et al, 1987;Audet et al, 1994;Larrive e et al, 1998). Additional contractility experiments were designed to monitor the e ect of the inhibition of protein synthesis on the depression of the maximal agonist e ect induced by B-9858.…”