Biomedical subjects

F Marceau

Publications and source records attributed to F Marceau.

At least 73 records · Page 4Linked to original sources

PubMed1992

Effects of interleukin-1 receptor antagonist on three types of responses to interleukin-1 in rabbit isolated blood vessels.

Interleukin-1 receptor antagonist (IRA) is a secretory product of human monocytes or related cell lines that acts as a pure interleukin-1 (IL-1) antagonist in several bioassays. IRA administration was reportedly a life-saving intervention in rabbits injected with lethal doses of bacterial lipopolysaccharide (LPS). We report the inhibitory effect of IRA on three distinct types of vascular responses to IL-1 in rabbit isolated blood vessels. The rabbit isolated superior mesenteric artery, when precontracted with phenylephrine, relaxed in a sustained manner in less than 30 min following application of recombinant interleukin-1 beta (12-290 pM), and this was a prostaglandin (PG)-dependent and endothelium-independent process. IRA (human recombinant sequence; 0.9-15 nM) behaved as an antagonist of IL-1 alpha or IL-1 beta, based on the surmountability and the concentration dependence, but could only prevent the effect of IL-1, not reverse it. IRA had no direct effect on the preparation and did not influence the acute relaxing effect elicited by substance P or iloprost, a PGI2 mimetic. Exposure to IL-1 beta depressed the response to noradrenaline (NA) in several hours in rabbit aorta rings. The inhibitory effect of IL-1 beta was endothelium and prostaglandin independent, but was prevented by a treatment with NG-nitro-L-arginine (a nitric oxide synthesis inhibitor), cycloheximide, dexamethasone, or IRA. Using the residual NA-induced contraction as a quantification of the IL-1 agonist effect, IRA was a very potent antagonist of IL-1 beta but was not totally surmountable.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1991

Human interleukin-1 induces a rapid relaxation of the rabbit isolated mesenteric artery.

1. Strips of rabbit superior mesenteric artery, precontracted with phenylephrine, relaxed when exposed to human recombinant interleukin-1 (IL-1) of the alpha or beta types. The effect was observed within 10 min, was optimal 32 min after the application of the cytokines and concentration-dependent (12-290 pM). 2. IL-1 alpha and IL-1 beta were equipotent in relaxing the rabbit mesenteric artery. A synthetic fragment corresponding to IL-1 beta 163-171 was approximately one million fold less active than IL-1 beta. The tripeptide Lys-D-Pro-Thr, an analogue of IL-1 beta 193-195, was inactive as an antagonist of IL-1 beta on the preparation. 3. Indomethacin (2.8 microM) prevented or acutely reversed IL-1-induced relaxations in the rabbit mesenteric artery. Purified haemoglobin (10 microM) or the removal of endothelium had no effect on relaxations elicited by IL-1 beta. 4. The preparation exhibited some selectivity for IL-1 as recombinant human tumour necrosis factor-alpha (TNF-alpha), IL-2 or IL-6 failed to influence it. TNF-alpha was not synergistic with a subthreshold concentration of IL-1 beta. 5. Immunoreactive 6-keto-prostaglandin F1 alpha and prostaglandin E2 were increased in the bathing fluid of isolated mesenteric arteries exposed to IL-1 beta as compared to controls. 6. A supernatant of lipopolysaccharide-stimulated human monocytes produced a relaxation of the preparation with a profile similar to that produced with IL-1s and there was a good quantitative agreement between the extent of the relaxation and the enzyme immunoassay measurements of IL-1 alpha and IL-1 beta in the supernatant.Furthermore the relaxation of crude monocyte IL-i was prevented by preincubating with antibodies to IL-l alpha and IL-1 beta. This experiment illustrates the possible use of the preparation for bioassay of IL-1. 7. It is concluded that either form of IL-I relaxes the precontracted rabbit mesenteric artery by a prostaglandin-dependent, nitric oxide-independent mechanism. The model is also useful for distinguishing the mechanism of IL-1-induced hypotension in vivo in rabbits.

Animals↗

PubMed1991

Pulse exposure to protein synthesis inhibitors enhances vascular responses to des-Arg9-bradykinin: possible role of interleukin-1.

1. The modulation of the spontaneous increase in contractile responses to des-Arg9-bradykinin (des-Arg9-BK) of rabbit aortic strips incubated in vitro was studied. Rapid hypotensive responses to exogenous kinins were also measured in rabbits anaesthetized 5 h following pretreatment. 2. Continuous exposure to the protein synthesis inhibitors cycloheximide (71 microM) or anisomycin (3.8 microM) profoundly inhibited the sensitization to des-Arg9-BK in incubated aortic strips. However, temporary (3 h) inhibition of protein synthesis in vitro followed by further incubation (3 h) of tissues without inhibitor, paradoxically enhanced both the maximal contractile responses to des-Arg9-BK (1.7 microM) and the apparent affinity of the kinin without affecting contractions to noradrenaline (NA, 100 nM) at 6.5 h. 3. The stimulatory activity of the short treatment (pulse) with cycloheximide was abolished in the presence of dexamethasone sodium phosphate (100 microM throughout the incubation). The function of receptors for kinins did not appear to be altered directly by the steroid treatment. 4. Interleukin-1 beta (IL-1 beta), applied at low concentrations (100-250 pg ml-1) on aortic strips between 3 h and 6.5 h of incubation time, mimicked the selective stimulatory effect of the cycloheximide pulse on responses to des-Arg9-BK. Higher concentrations of IL-1 beta (0.5-5 ng ml-1) did not further amplify the responses to des-Arg9-BK but decreased the contractile responses to NA. 5. The modulation by IL-1 beta of vascular sensitivity to des-Arg9-BK and to NA was prevented by blockade of protein synthesis. 6. The induction in vivo by IL-1 beta (5 micrograms kg-1) or by cycloheximide (10 mg kg-1) of cardiovascular responsiveness to des-Arg9-BK was demonstrated with a blood pressure assay of exogenous kinins or with tissues isolated ex vivo 5 h after pretreatment of animals. Evidence of active disposition of cycloheximide in vivo was also obtained. 7. We propose the production of endogenous IL-1 as a possible mechanism for the enhancement of responsiveness to des-Arg9-BK observed in tissues pulsed with a protein synthesis inhibitor and for the inducing effect of cycloheximide or E. coli lipopolysaccharide in vivo. These results suggest that effects mediated by the BK1 receptor for kinins are potentially present in pathological conditions associated with IL-1 production.

Animals↗

PubMed1991

The interaction of 3,5-pyrazolidinedione drugs with receptors for f-Met-Leu-Phe on human neutrophil leukocytes: a study of the structure-activity relationship.

The 3,5-pyrazolidinedione (3,5-P) drugs, phenylbutazone and sulfinpyrazone, have been reported to bind to receptors for the chemotactic peptide, f-Met-Leu-Phe, and to behave as functional antagonists of f-Met-Leu-Phe in human and rabbit neutrophils. To explore the structure-activity relationship of this family of drugs for f-Met-Leu-Phe receptor binding, 36 drugs with the 3,5-P structure, a structure related to antipyrine, or an unrelated structure were tested as competitors for the binding of f-Met-Leu-Phe-Lys-fluorescein isothiocyanate on human neutrophils by flow cytometric analysis. Only drugs possessing the 3,5-P ring were significant competitors. The five most potent 3,5-Ps behaved as selective antagonists of f-Met-Leu-Phe-induced superoxide anion release by neutrophils. The potency was not correlated to the pKa or to their capacity to inhibit prostaglandin E2 released from culture fibroblasts but instead appeared to be correlated to their apparent octanol-buffer partition coefficients. The most potent f-Met-Leu-Phe antagonist identified, 1,2-diphenyl-4-(3-(1-naphthyl)-propyl)-3,5-pyrazolidinedione (DPN), may also possess an improved pharmacodynamic specificity compared with phenylbutazone and sulfinpyrazone, as it was less potent than phenylbutazone in the inhibition of prostaglandin synthesis and it was not cytotoxic. DPN may be a prototype for a valuable new class of anti-inflammatory drugs.

Binding, Competitive↗

PubMed1991

Relaxant effect of chemotactic peptides on rabbit vascular strips: evidence for nitric oxide release from a nonendothelial source.

Two distinct peptides, C5a and f-Met-Leu-Phe (FMLP), that are chemotactic for phagocytic leukocytes affect profoundly the circulation in various in vivo systems. These peptides are known to relax strips of rabbit isolated blood vessels, the portal vein and pulmonary artery. In the present study, the effect of recombinant human C5a (2.5-25 nM) was examined and found to be qualitatively similar to that previously reported for FMLP. Indomethacin completely or partially inhibited the vasorelaxations induced by either peptide in the pulmonary artery and the portal vein, respectively. The relaxation induced by C5a was not abolished by removing the endothelial lining of the model vessels. The C5a or FMLP effects were more tachyphylactic in tissues continuously exposed to cycloheximide; this phenomenon was particularly pronounced for FMLP. A series of experiments were focused on the indomethacin-resistant component of the relaxation induced by either peptide on the portal vein. This component was not inhibited by capsaicin pretreatment or by endothelium removal, but was suppressed by treatment with NG-nitro-L-arginine or reduced by LY-83583. These findings suggest that the chemotactic peptides elicit their mechanical effect on rabbit vascular smooth muscle through the release of secondary mediators not related to the endothelium; the mediators are tentatively identified as prostaglandins and nitric oxide. It is the coordinated combinations of the metabolic pathways that are involved in the final responses, with inherent differences between vessel sources and the agonists used.

Animals↗

PubMed1991

Hypotensive effects of Lys-des-Arg9-bradykinin and metabolically protected agonists of B1 receptors for kinins.

B1 receptors for kinins are selectively stimulated by bradykinin (BK) or Lys-BK (kallidin) fragments without the C terminal arginine residue. The present study was performed using an established in vivo model of B1 receptor-mediated cardiovascular action. Rabbits pretreated with bacterial lipopolysaccharide (LPS) (25 micrograms/kg) and anesthetized 5 h later exhibit acute and transient hypotension in response to intra-arterial boluses of B1 receptor agonists. The naturally occurring B1 agonist Lys-des-Arg9-BK was more potent than des-Arg9-BK in the in vivo model, but the effect of either natural sequence was brief. Evidence derived from previous in vitro experiments suggests these peptides may be substrates for angiotensin I converting enzyme (ACE). In addition, Lys-des-Arg9-BK is hydrolyzed in vitro by aminopeptidase M. Therefore, we tested the hypotensive effects of Lys-des-Arg9-BK analogs selectively protected against ACE activity (Lys-[D-Phe8]des-Arg9-BK) or against both ACE and aminopeptidase M (Sar-[D-Phe8]des-Arg9-BK). Both analogs were found to elicit a biphasic response consisting of a brief hypotensive effect followed by a prolonged hypotensive state. Indomethacin prevented only the second, prolonged phase of the hypotension induced by the metabolically protected analogs. The duration of hypotensive episodes induced by Lys-des-Arg9-BK was increased in rabbits pretreated with either captopril, an ACE inhibitor, or the aminopeptidase M inhibitor amastatin, consistent with the prolonged effect of metabolically protected analogs. An infusion of the B1 agonist Sar-[D-Phe8]des-Arg9-BK (1 microgram/min) in lipopolysaccharide-pretreated rabbits led to a very important and persistent hypotensive state that was not prevented by indomethacin.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗

PubMed1990

Long-term culture and characterization of human limbal microvascular endothelial cells.

Human limbal explants obtained from 44 eyebank donors were cultured in medium 199 supplemented with 20% fetal bovine serum, vascular endothelial cell growth supplement and heparin. Cells grew abundantly out of the explants. They initially formed a 'cobblestone' patterned monolayer but later exhibited an elongated morphology with growth in parallel bundles. These cells could be passaged at least nine times and were identified throughout the consecutive passages as microvascular endothelial cells by the expression of factor VIII-related antigen, laminin and of the H determinant of ABO blood groups. As expected from vascular endothelial cells, flow cytometric analysis demonstrated a strong expression of class I histocompatibility antigens and a weaker expression of class II antigens. Class II antigen expression was enhanced by culturing the cells in the presence of immune interferon. These cells produced immunoreactive interleukin-1, mainly of the alpha type, under endotoxin stimulation. Limbal microvascular cells could be useful to study corneal angiogenesis. Furthermore, long-term culture of limbal cadaveric tissue can potentially be used to characterize donor-specific immunologic responses in corneal graft recipients.

ABO Blood-Group System↗

PubMed1990

Bacitracin U.S.P. contains a factor that stimulates receptors for 5-hydroxytryptamine on rabbit aortic strips.

Bacitracin (BAC) U.S.P., obtained in the form of sterile powder, elicits dose-dependent and non-tachyphylactic contractions of the rabbit isolated aorta and of other rabbit vessels. The use of several pharmacologic antagonists suggests that BAC is a 5-hydroxytryptamine mimetic in aortic strips, since the antibiotic is competitively antagonized by methysergide and ketanserin with pA2 values compatible with an agonist action on the 5-HT2 receptors found in the aortic preparation. It remains to be determined whether bacitracin A, the chief constituent of BAC U.S.P., is the 5-HT agonist.

Animals↗

PubMed1990

Contractile effect of the chemotactic factors f-Met-Leu-Phe and C5a on the human isolated umbilical artery. Role of cyclooxygenase products and tissue macrophages.

Factors that are chemotactic for phagocytic leukocytes are known to elicit important acute circulatory changes, and the role of circulating leukocytes in these models is controversial. To evaluate the role of the blood vessel wall in the absence of circulating cells, spiral strips of human umbilical artery were exposed in vitro to the chemotactic peptides f-Met-Leu-Phe (1-100 nM) or C5a (2.5-25 nM). Contractile responses were observed for both peptides. Certain agonist analogues and a selective antagonist of the chemotactic action of f-Met-Leu-Phe behaved correspondingly as agonists and antagonist of the contractile effect on umbilical artery. The anaphylatoxin C3a also exerted a contractile effect on the tissue (25 nM and above), but this effect was highly tachyphylactic. Inhibitory drugs were used to examine the contributions of secondary mediators in eliciting the effects of C5a and f-Met-Leu-Phe. The contractile effect of both peptides was massively inhibited either by indomethacin or the thromboxane A2/prostaglandin H2 antagonist SQ 29548. Dazmegrel, a thromboxane A2 synthetase inhibitor, had partial inhibitory effects on contractions induced by either peptide. The contractile effect of C3a was prevented by indomethacin pretreatment. Vascular strips did not release measurable histamine in the bathing fluid after challenge with C5a or f-Met-Leu-Phe. The tissue apparently contains neither histamine nor mast cells. Autoradiography of 125I-labeled C5a or f-Met-Leu-Phe analogue showed specific binding of the peptides to cells dispersed in the vessel wall, but more frequently at the periphery. Cells stained positively for alpha-naphthyl acetate esterase showed a similar distribution. Pure cultures of smooth muscle cells derived from the umbilical artery failed to release prostanoids when exposed to f-Met-Leu-Phe or C5a, whereas fresh strips of this artery released more thromboxane B2 than the baseline in response to these peptides. We conclude that macrophagelike cells, present in the vessel wall, are the likely target cells for the chemotactic peptides. These cells trigger a contractile effect of the smooth muscle by generating cyclooxygenase products.

Anaphylatoxins↗

PubMed1989

Prostacyclin release induced by neurokinins in cultured human endothelial cells.

The effects of neurokinins (NK) and related peptides on the secretion of 6-keto-prostaglandin F1 alpha, a stable metabolite of prostacyclin, were measured. These peptides enhanced three- to five-fold the basal secretion rate with the following rank order of potency (based on threshold concentrations for a significant output): substance P (SP) greater than or equal to NKA greater than SP 4-11 greater than or equal to [pGlu6]SP 6-11 = SP 7-11.NKB and SP 1-9 were inactive. Ac[Arg6, Sar9, Met(O2)11]SP, a NK1 receptor selective agonist, was more potent than other selective agonists for the NK2 and NK3 receptor subtypes. These results suggest that the NK receptors, which mediate the release of prostacyclin from human endothelial cells, belong to the NK1 subtype.

6-Ketoprostaglandin F1 alpha↗

PubMed1989

Relaxant effect of N-formyl-methionyl-leucyl-phenylalanine on rabbit vascular strips.

Some types of rabbit isolated blood vessels precontracted with phenylephrine relaxed when exposed to the chemotactic peptide N-formyl-Met-Leu-Phe (FMLP). The thoracic aorta was unresponsive whereas the portal vein and pulmonary artery exhibited concentration-dependent relaxing responses to FMLP (1-100 nM). FMLP-induced relaxations developed over several minutes and occurred after a latency of 30 to 40 sec. An inconsistent, brief and small contractile phase preceded the relaxations in some tissues. Stable responses to FMLP could be obtained repeatedly at 1.5-hr intervals. On both the portal vein and the pulmonary artery, the structure-activity relationship of peptides related to FMLP was similar to the one reported for activating phagocytic leukocytes. The peptide Boc-Phe-D-Leu-Phe-D-Leu-Phe behaved as a competitive antagonist of FMLP-induced relaxations with a calculated pA2 of 7.5 on both types of responsive vessels. Indomethacin inhibited the relaxations completely on the pulmonary artery and partially on the portal vein. FMLP-induced vasorelaxations were unaffected by a platelet-activating factor antagonist, BN 52021, or a 5-lipoxygenase inhibitor, L-651,392. Removal of the endothelium did not prevent the relaxant response to FMLP. The release of 6-keto-prostaglandin F1 alpha in the bathing fluid of portal vein and pulmonary artery exposed to FMLP was demonstrated using a radioimmunoassay. FMLP relaxed rabbit vascular strips in a blood-free environment by releasing secondary mediators tentatively identified as prostaglandins; however, a component of the relaxation in the portal vein was not mediated by cyclooxygenase products.

6-Ketoprostaglandin F1 alpha↗

PubMed1988

Studies on the effects of disease-modifying antirheumatic drugs on lipoxygenase product synthesis in human neutrophils in vitro.

The disease-modifying antirheumatic drugs sodium aurothiomalate, D-penicillamine and chloroquine phosphate were tested on leukotriene (LT) synthesis in human blood polymorphonuclear leukocytes stimulated with either the ionophore A23187, zymosan or f-Met-Leu-Phe. Lipoxygenase products were analyzed by reversed-phase high-performance liquid chromatography. The study demonstrated that the drugs can either inhibit or enhance 5-lipoxygenase product synthesis in human leukocytes, depending on the stimulus used to activate the cells and the drug concentration. The data also suggested that increased substrate availability accounted for the stimulatory effects of the drugs on leukotriene synthesis.

Anti-Inflammatory Agents, Non-Steroidal↗

PubMed1988

Effect of glucocorticoids, monokines and growth factors on the spontaneously developing responses of the rabbit isolated aorta to des-Arg9-bradykinin.

1. The mechanisms modulating the spontaneous induction of contractile responses to agonists of the B1-receptors for kinins have been studied by submitting the rabbit isolated aorta preparation to various in vitro treatments. Des-Arg9-bradykinin (Des-Arg9-BK), applied after 6 h of in vitro incubation was the standard stimulus to monitor this up-regulation process. 2. Specific inhibition of the development of the contractile response to des-Arg9-BK was obtained by exposing tissues continuously to dexamethasone, dexamethasone sodium phosphate (DSP) or cortisol, but not to oestradiol. The maximal extent of the inhibition obtained at high concentrations of glucocorticoids was 86%. 3. No gross inhibition of protein synthesis was observed in the presence of DSP as monitored by [35S]-methionine incorporation into incubated pieces of rabbit aorta. 4. In vivo pretreatment of rabbits with DSP did not reduce further the development of the responses in vitro. DSP applied 15 min before the 6 h recording did not antagonize the contractile effect of the BK fragment. 5. Interleukin 1 (IL-1) and interleukin 2 (IL-2) applied in vitro for the first 3 h of incubation increased the development of the contractile response to des-Arg9-BK. 6. Arachidonic acid (AA), nordihydroguaiaretic acid, tumour necrosis factor-alpha (TNF) and transforming growth factor-beta (TGF-beta) failed to influence the spontaneous development of the response to kinins. 7. Continuous exposure to DSP (100 microM) markedly inhibited the action of stimulants in this system: IL-1, IL-2, epidermal growth factor and muramyl dipeptide. Moreover, the presence of AA (30 microM) did not prevent the inhibitory effect of DSP (100 microM). 8. None of the treatments applied singly or in combination modified the contractile response of the rabbit aorta to noradrenaline. 9. The results are discussed in terms of the possible involvement of immunocompetent cells in the up-regulation of vascular responsiveness to B, receptor agonists.

Animals↗

PubMed1988

Small fibronectin fragments induce endothelium-dependent vascular relaxations.

Strips of rabbit thoracic aorta precontracted with phenylephrine relaxed when exposed to selected synthetic peptides derived from the cell attachment domain of fibronectin. The relaxations elicited by both acetylcholine and the hexapeptide Gly-Arg-Gly-Asp-Ser-Pro (GRGDSP) were dependent on the presence of an intact endothelium, were resistant to indomethacin, and were inhibited by hemoglobin. The structure-activity relationship of four oligopeptides derived from fibronectin was in fair agreement with their ability to prevent fibronectin-mediated cell adhesion in other experimental systems. Human plasma fibronectin (up to 2.3 microM) did not relax this preparation and did not prevent the relaxant effect of the synthetic hexapeptide GRGDSP. On the rabbit isolated mesenteric artery, the relaxations induced by GRGDSP were significantly inhibited by indomethacin treatment, suggesting a contribution of locally produced prostaglandins. The displacement of fibronectin by soluble peptides from its binding sites on endothelial cells may result in significant pharmacologic responses, probably resulting from perturbations of the endothelial cell membranes.

Acetylcholine↗

PubMed1987

The ability of des-Arg9-bradykinin to relax rabbit isolated mesenteric arteries is acquired during in vitro incubation.

Strips of rabbit mesenteric arteries precontracted with phenylephrine relaxed when exposed to des-Arg9-bradykinin (BK), a typical B1 receptor agonist. We showed that the ability of des-Arg9-BK to relax this preparation was acquired during in vitro incubation and was abolished by cycloheximide treatment. In this preparation intimal damage reduced but did not abolish the relaxant effect of des-Arg9-BK, and indomethacin uncovered a contractile effect of des-Arg9-BK also acquired during the in vitro incubation.

Animals↗

PubMed1987

Carboxypeptidase N (kininase I) activity in blood and synovial fluid from patients with arthritis.

Carboxypeptidase N (CPN, kininase I) and kininase II (angiotensin converting enzyme) activities were measured simultaneously in blood plasma and synovial fluid in patients suffering from rheumatoid arthritis (RA), psoriatic arthritis (PA) and osteoarthritis (OA) and in the plasma of normal volunteers. CPN levels (defined as the rate of hydrolysis of furylacryloyl-Ala-Lys) in blood were modestly increased and correlated with erythrocyte sedimentation rate in RA and PA. Based on the hydrolysis of synthetic substrates, CPN activity was much higher than kininase II activity in synovial fluid (SF). SF kininase activities were always inferior to the blood levels in all patients and were correlated with the logarithm of SF leukocyte counts, an indicator of the intensity of inflammation. In addition, CPN and albumin levels in SF were highly correlated when expressed as a percent of the plasma concentrations. Biochemical properties of CPN in crude SF confirmed its similarity to blood CPN. Polymorphonuclear leukocytes derived from inflammatory SF did not release CPN. It is concluded that kininases diffuse from the blood into SF through increased vascular permeability and that CPN could be a major metabolic pathway for kinins in this form of exudate. CPN leads to the formation of des-Arg kinins, selective agonists of the B1 receptors for kinins.

Arthritis↗

PubMed1987

Effects of low molecular weight fibrin degradation products 6A and 6D on rabbit aorta strips.

Two small molecular weight fibrin degradation product, the pentapeptide 6A and the undecapeptide 6D, produced relaxations of norepinephrine-contracted rabbit aorta strips. The relaxations were slow-developing and were elicited by both peptides at supramicromolar concentrations; the amplitude of relaxations were small for 6D. The relaxations induced by 6A were not dependent on the presence of endothelium and were not modified by a mixture of indomethacin, pyrilamine, and cimetidine. The amplitude of the relaxations produced by 6A and 6D increased as a function of incubation time in vitro. In another experimental system, peptides 6A and 6D failed to increase 6-keto-PGF1 alpha release from cultured human umbilical endothelial cells. Histamine and bradykinin were both active in this system.

6-Ketoprostaglandin F1 alpha↗

PubMed1987

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

1 The mechanisms by which agents modulate the induction of kinin B1-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 of the 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 microM). 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; 1 micrograms ml-1), muramyl-dipeptide (MDP; 2 micrograms ml-1), phorbol myristate acetate (PMA; 320 nM), epidermal growth factor (EGF; 100 ng ml-1) and endothelial cell growth factor (150 micrograms ml-1). 4 The protease inhibitors phenylmethylsulphonyl fluoride and aprotinin, a non-adjuvant isomer of MDP, rabbit purified leukocyte interferon, fibroblast growth factor and the chemotactic peptide N-formyl-L-methionyl-L-leucyl-L-phenylalanine (FMLP) did not have this effect. 5. It has been demonstrated that LPS induces B1-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 micrograms) and PMA (100 micrograms) were also found to induce a state of responsiveness to des-Arg9-Bk in vivo. FMLP (1 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.

Anesthesia↗