Interaction of bradykinin with substance P on vascular permeability and pain response

Combination of bradykinin with substance P exerted synergistic effects on vascular permeability and pain response in mouse paw. Denervation of sciatic nerve reduced significantly bradykinin-induced vascular permeability, suggesting the involvement of sensory nerves. The bradykinin-induced vascular permeability was also reduced by intravenous injection of a substance P-antagonist. The results suggest that neuronal substance P takes part in the action of bradykinin on inflammation and pain sensation.     

Decreased cAMP content of the hypothalamus of genetically hypertensive rats

Summary In genetically hypertensive rats an altered catecholamine content of hypothalamic structures has been reported. In the present study cAMP was estimated in the hypothalamus and cortex of genetically hypertensive rats and compared with normotensive controls of the same strain. It is shown, that the cAMP content of the hypothalamus of the hypertensive animals was decreased to about 60% of control values, whereas there was no difference of the cAMP content in the cortical regions of the same animals. These results indicate an alteration of the adenyl cyclase-cAMP-phosphodiesterase system in hypothalamic structures of genetically hypertensive rats.Supported by the Deutsche Forschungsgemeinschaft     

Altered vascular permeability responses to substance P in diabetic rats: Interactions with a nitric oxide synthesis inhibitor

The effect of inhibiting nitric oxide synthase (N^ω-nitro-L-arginine) on plasma extravasation induced by intravenously administered substance P, [pGlu⁵,Me-Phe⁸,Sar⁹]substance P-(5–11) or prostaglandin E₂ was examined. Control rats were more responsive than diabetic rats to both substance P and [pGlu⁵,Me-Phe⁸,Sar⁹]-substance P-(5–11). N^ω-Nitro-L-arginine blocked the actions of substance P on dorsal skin, but potentiated those of [pGlu⁵,Me-Phe⁸,Sar⁹]substance P-(5–11) in control rats. In diabetic rats N^ω-nitro-L-arginine, which did not affect the actions of the substance P analogue, exerted complex effects on substance P induced plasma extravasation giving potentiation in the tongue, inhibition in bronchioles, and no effect in other tissues. N^ω-Nitro-L-arginine inhibited prostaglandin E₂ induced extravasation in control, but not diabetic rats. The altered plasma extravasation in diabetic rats may be due to diabetes induced alterations in nitric oxide synthesis or in the responses of the endothelial cells to nitric oxide.     

Major metabolites of substance P degraded by spinal synaptic membranes antagonize the behavioral response to substance P in rats

Substance P (SP) was degraded by synaptic membranes of rat spinal cord. Cleavage products were separated by reversed phase high performance liquid chromatography and identified by amino acid composition analyses. Major products of SP were phenylalanine, SP(1-4), SP(1-6), SP(1-7), SP(10-11), and SP(8-9). Both the degradation of SP and the accumulation of the major cleavage products were strongly inhibited by a metal chelator, o-phenanthroline, and also by specific inhibitors of endopeptidase-24.11, thiorphan, and phosphoramidon. Thus, endopeptidase-24.11 plays a major role in SP degradation in the rat spinal cord. N-Terminal fragments, SP(1-7) and SP(1-4), detected after incubation with spinal synaptic membranes were examined in vivo for antagonism against the scratching, biting, and licking response induced by intrathecal (IT) injection of SP (3.0 nmol) in rats. When IT coadministered with SP, SP(1-7) and SP(1-4) produced a significant inhibition of behavioral response to SP with ED50 of 135.0 pmol and 6.2 nmol, respectively. These results suggest that the degradation of SP in the spinal cord is not only responsible for inactivation of parent peptide, but may also lead to the formation of N-terminal SP-fragments which are shown to display a novel physiological function.     

Renal vascular reactivity to P(2)-purinoceptor activation in spontaneously hypertensive rats

This study was performed to determine the possible contribution of an imbalance between P(2X) (vasoconstriction) and P(2Y) (vasodilation)-purinergic reactivity to the increased vascular resistance of spontaneously hypertensive rats (SHR). The vasoactive responses to alpha,beta-methylene ATP and 2-methylthio ATP specific agonists, respectively, for P(2X) and P(2Y) purinergic receptors were characterized in isolated perfused kidneys from Wistar Kyoto (WKY) and SHR. To analyze P(2X)- and P(2Y)-purinergic reactivity we used phenylephrine and barium chloride, or acethylcholine (ACh) and sodium nitroprusside (NP) as reference compounds, respectively. The renal vasculature from SHR showed markedly enhanced reactivity to alpha,beta-methylene ATP, phenylephrine and barium chloride. The dose-response curves were characterized by a similar threshold, with a greater maximal response. There were no significant differences in the dose-response curves or in maximal vasodilation to 2-methylthio ATP, ACh or NP when both groups were compared, except at the dose of 10(-6) g/g kidney weight of NP in which the SHR group showed an increased responsiveness. The results indicate that the increased responsiveness of kidneys from SHR to alpha,beta-methylene ATP may be due to nonspecific functional changes in the renal vasculature rather than to a specific alteration in the activity of renal P(2X)-purinoceptors. Our results also indicate that P(2Y)-purinergic reactivity, nitric oxide-induced vasodilation and the cGMP-dependent mechanisms of vasodilation are well preserved in SHR.     

The vascular response to the K+ channel inhibitor 4-aminopyridine in hypertensive rats

The K+ channel inhibitor 4-aminopyridine induced an immediate increase in blood pressure and tension in spontaneously hypertensive rats (SHR). Further analysis strongly suggested this to be due to closure of vascular smooth muscle K+ channels, as previously concluded for normotensive rats (WKY). The tension response was greater in SHR than WKY, suggesting an increased channel activity in order to compensate for the high total peripheral vascular resistance in SHR. The response was enhanced after nitric oxide (NO) synthase inhibitor in both strains, probably reflecting increased channel activity after elimination of the NO-cGMP pathway. The response in SHR but not WKY was increased after alpha(1)-adrenoceptor inhibition and adrenalectomy but not sympathetic nerve transmitter depletion. It increased also after angiotensin AT(1) and endothelin ET(A) receptor antagonists and protein kinase C inhibitor. These results indicated an increased adrenal catecholamine, angiotensin AT(1) and endothelin ET(A) activation of the phospholipase C-protein kinase C pathway in SHR, inhibiting the 4-aminopyridine-sensitive K+ channels.     

Acute tobacco smoke-induced airways inflammation in spontaneously hypertensive rats

Common laboratory rats and mice fail to develop persistent, progressive pulmonary inflammation found in chronic obstructive pulmonary disease as a result of tobacco smoke exposure. We hypothesized that spontaneously hypertensive rats would be more susceptible than normal Wistar Kyoto rats to acute tobacco smoke-induced pulmonary inflammation due to impaired apoptosis. Spontaneously hypertensive rats display systemic oxidative stress, inflammation, hypercoagulation, and immunosupression, similar to humans with chronic obstructive pulmonary disease. Male spontaneously hypertensive rats and Wistar Kyoto rats were exposed whole-body to tobacco smoke (total particulate concentration 75-85 mg/m(3)) or filtered air for 6 h/day for 2 or 15 days (3 days/wk). Tobacco smoke caused an increase in bronchoalveolar lavage fluid neutrophils at both time points in each strain. Significantly more neutrophils were noted in spontaneously hypertensive rats at 15 days compared to Wistar Kyoto rats. There was a trend of increase for macrophages in spontaneously hypertensive rats at both time points (significant at 2 days). TUNEL assay detected apoptotic cells in bronchoalveolar lavage fluid and lung tissue sections. The number of apoptotic neutrophils in airway walls and bronchoalveolar lavage fluid increased at 2 days in both strains, but at 15 days the effect was much lower in spontaneously hypertensive rats than in Wistar Kyoto rats. Tobacco smoke induces a greater inflammatory response associated with lower apoptotic neutrophils in the lungs of spontaneously hypertensive rats compared to Wistar Kyoto rats. The spontaneously hypertensive rat may be a more relevant animal model of acute tobacco smoke-induced airway inflammation than other laboratory rats.     

Studies on the vascular permeability induced by intrathecal substance P and bradykinin in the rat.

The effects of substance P (SP), SP fragments, neurokinin A (NKA), neurokinin B (NKB) and selective agonists for neurokinin receptors were assessed on cutaneous vascular permeability after intrathecal (i.t.) administration in rats. Dose-dependent increases in plasma extravasation were observed with the following rank orders of potency ([p-Glu6]SP-(6-11) greater than SP greater than or equal to SP-(4-11) greater than [p-Glu5,MePhe8,Sar9]SP-(5-11) = [p-Glu5]SP-(5-11) greater than SP-(7-11) and SP greater than NKA greater than NKB). The N-terminal fragments SP-(1-4), SP-(1-7) and SP-(1-9) were inactive up to 65 nmol. The NK-1 receptor selective agonists [( beta-Ala4,Sar9,Met(O2)11]SP-(4-11) and [Pro9,Met(O2)11]SP) were more potent than the NK-2 ([Nle10]NKA-(4-10] and NK-3 ([beta-Asp4,MePhe7]NKB-(4-10) and [MePhe7]NKB) receptor-selective agonists. Plasma extravasation was also increased by i.t. bradykinin (BK, 8.1 nmol) while the fragment BK-(1-8), a potent B1-receptor-selective agonist, produced only a slight effect at 81 nmol. When BK was given after prior i.t. administration of 6.1 nmol of [Thi5.8,D-Phe7]BK, an antagonist of BK at the B2-receptor, the increase in vascular permeability was significantly attenuated. The analogue [Leu8]BK-(1-8) (10.3 nmol), an antagonist of BK at the B1-receptor, failed to modify the BK-induced plasma extravasation. Plasma extravasation induced by SP (6.5 nmol) and BK (8.1 nmol) was abolished in cervically vagotomized rats, and significantly reduced in both spinal rats and in capsaicin-treated animals. Conversely, bilateral adrenalectomy (48 h earlier) and intercollicular decerebration (30 min earlier) had no major effect on the response elicited either by SP or BK. The response to SP remained unaffected by methysergide and hexamethonium but was significantly reduced by methylnitrate atropine and diphenhydramine. Indomethacin significantly enhanced the plasma extravasation induced by SP. These results suggest that SP and BK may play a role as spinal mediators in peripheral vascular permeability through a sensory and cholinergic vagal mechanism involving a spinobulbar pathway. The receptors mediating the response to SP and BK in the spinal cord are of the NK-1 and B2 subtypes, respectively.     

Tachykinin substance P depletion by capsaicin exacerbates inflammatory response to sidestream cigarette smoke in rats

To evaluate the role of substance P (SP)-containing C-fiber nerves in the development of the inflammatory responses to sidestream cigarette smoke (SSCS), female Fischer 344 rats were randomly assigned into vehicle and capsaicin groups, respectively. Then, half the number in each group (N = 24) was nose-only exposed to air or 0.4 mg/m3 total particulate matter of SSCS for 4 h/day for 7 days. Exposure of the vehicle rats to SSCS induced obvious pulmonary neurogenic inflammation as indicated by elevations in plasma extravasation and proinflammatory cytokine secretions [interieukin (IL)-1beta and IL-12]. In addition, except for SP release, SSCS exposure significantly induced the tachykininergic toxicities at the gene level: upregulation of beta-preprotachykinin-I (beta-PPT-I) mRNA. However, neither SSCS exposure nor capsaicin pretreatment affects the immunolabeling density of neurokinin-1 receptor (NK-1R) in airway epithelium. SSCS also significantly inactivated pulmonary neutral endopeptidase (NEP) in lung tissue. Moreover, pretreatment with capsaicin significantly exacerbated the SSCS-induced inflammatory responses mentioned above as well as the release of plasma protein. Considering that capsaicin did not affect the normal control baselines of these parameters except for a decrease in NK-1R mRNA, we conclude that the degree of SSCS-induced inflammatory response was exacerbated because of the depletion of stored SP and/or inactivation of capsaicin-sensitive C-fiber nerves. Our data suggest the loss of afferent tachykinin SP signaling may lead to dysfunction of the sensory C-fiber nerve reflexes during exposure to SSCS, suggesting that SP serves a protective role.     

Remodelling of mesenteric arteries in genetically hypertensive rats cross-fostered from birth to normotensive Wistar rats

1. The effects of cross-fostering genetically hypertensive (GH) with normotensive (N) Wistar rats on the structure of mesenteric resistance arteries (MRA) in young (6 week old) and adult (18 week old) rats were investigated to see whether the abnormal remodelling known to exist in GH rats could be prevented by changing the maternal environment. 2. Genetically hypertensive and normotensive rat pups were reared either by their natural mothers or a foster mother of the opposite strain (NX and GHX) with fostering done within 24 h of birth. 3. Blood pressure (BP) was measured from age 6-18 weeks; at 6 and 18 weeks MRA structure was assessed. 4. At the time of death, intra-arterial mean BP was measured (via the femoral artery), after which MRA were fixed by perfusion (at the systolic BP of the rat) via the abdominal aorta, first with 75% Tyrode's solution containing heparin and papaverine, followed by 2% glutaraldehyde in 75% Tyrode's solution. Arteries were dissected out, processed and embedded in Technovit (Heraeus Kulzer, Werheim, Germany) and serial sections were cut and stained with Giemsa. 5. Stereological techniques were used to determine media width, lumen diameter and medial cross-sectional area (CSA); in addition, the ratio of media width to lumen diameter was calculated. Smooth muscle cell density was also calculated. 6. In MRA from 6-week-old rats, GH rats compared with N rats had increased media width and CSA and an increased ratio of media width to lumen diameter. 7. There were no significant changes in structure in the GHX group compared with GH rats. The NX group compared with N rats had increased media width and CSA and lumen diameter, but no change in the ratio of media width to lumen diameter. Smooth muscle cell density, reduced in GH compared with N rats, was increased (P < 0.001) in the NX group, but not changed in the GHX group compared with GH rats. 8. In 18-week-old GH rats compared with N rats, the MRA had a decreased media width and medial CSA and smaller lumen diameter, but there was no change in the ratio of media width to lumen diameter. 9. In the GHX group compared with GH rats, media width and CSA were reduced; in the NX group compared with N rats, media width was increased, lumen decreased and the ratio of media width to lumen diameter increased. Smooth muscle cell density was increased (P < 0.001) in the GHX group, but not in the NX group. 10. Changing the maternal environment significantly affected BP in GHX and NX groups up to 9-10 weeks of age but, in adult rats, the BP differences were no longer present. Thus, structural changes were seen at 6 weeks of age in MRA from NX rats and also at 18 weeks in GHX and NX rats (even though the BP differences were no longer significant); structural remodelling occurred independently of BP.     

四逆汤对肾性高血压大鼠血压的调节作用和机制

目的探讨四逆汤对肾性高血压大鼠血液内血管活性物质含量和主要靶器官血管活性物质表达的调节作用。方法健康♀Wistar大鼠24只,随机分为伪手术(SO)组、肾性高血压(RH)组和四逆汤治疗(ST)组,每组8只。根据双肾动脉夹闭法建立肾性高血压动物模型,应用RBF-2型大鼠尾动脉血压计测量血压,硝酸还原酶比色法测定血清中一氧化氮(NO)含量,放射免疫法测定血浆中内皮素(ET)、降钙素基因相关肽(CGRP)和血管紧张素Ⅱ(AngⅡ)的含量。免疫组化法测定心、脑、肾组织内皮素受体A(ETRA)、一氧化氮合酶(NOS)、AngⅡ和CGRP的表达。结果①ST组大鼠血压明显低于RH组(P<0.05)。②大鼠血清NO、血浆CGRP和ET含量ST组均明显高于RH组(P<0.05),AngⅡ含量无变化(P>0.05)。③大鼠心、肾ETRA表达水平ST组均明显低于RH组(P<0.05),但脑组织中含量差异无显著性(P>0.05);心脏eNOS表达水平ST组明显高于RH组(P<0.05),脑、肾iNOS表达水平ST组明显低于RH组(P<0.05);心、脑、肾CGRP表达水平ST组均低于RH组(P<0.05);心、肾AngⅡ表达水平ST组均明显低于RH组(P<0.05),但在脑差异无显著性(P>0.05)。结论四逆汤可能通过调节肾性高血压大鼠心、脑、肾内血管活性物质的表达及其血液内的有效含量,而发挥血压调节作用。     

Role of bradykinin in the vascular permeability response induced by carrageenin in rats.

1 Bradykinin in carrageenin-induced inflammatory pouch fluid was measured by an enzyme immunoassay method. 2 The bradykinin showed a single peak in the 30-60 min period after the challenge and then decreased quickly, and there was a correlation between the bradykinin level and exudation of fluorescein-labelled bovine serum albumin in the first 60 min period. 3 Captopril (an inhibitor of kininase II) elevated both the bradykinin level in the inflammatory pouch fluid and vascular permeability, while DL-2-mercaptomethyl-3- guanidinoethylthiopropanoic acid (an inhibitor of kininase I) had no effect. 4 Soybean trypsin inhibitor (SBTI) inhibited the vascular permeability response in parallel with the decrease in the bradykinin level. 5 A bradykinin-degrading activity appeared in the pouch fluid within 1 h after the challenge and increased with time. 6 In the period of 3.5-4 h, bradykinin levels were suppressed below the sensitivity limit of the assay, i.e. 0.07 nm ml-1, in spite of active generation. This was because degradation of bradykinin was very rapid in this late stage. Nevertheless, bradykinin still played a definite role in sustaining a high level of vascular permeability response in the late stage in conjunction with prostaglandins.     

Cardiovascular effects of prazosin in normotensive and genetically hypertensive rats

1. The cardiovascular effects of prazosin, a new antihypertensive drug, were studied in normotensive and genetically hypertensive rats. 2. Prazosin, infused intra-arterially, lowered vascular resistance in the blood-perfused rat hind limb. This effect was dependent on the presence of intact sympathetic innervation to the limb; no direct vasodilatation was demonstrated. In this preparation prazosin infusion reduced vasoconstrictor responses to noradrenaline. 3. In the saline-perfused rat mesenteric artery preparation prazosin reduced responses to noradrenaline and sympathetic nerve stimulation but not those to serotonin and vasopressin. Prazosin was more potent than phentolamine, on a molar basis, in reducing the vasoconstrictor effects of noradrenaline. 4. A comparison of the effects of prazosin injected intravenously and into a lateral cerebral ventricle failed to show any central action of the drug on blood pressure. Experiments using the donor blood-perfused, vascularly isolated rat hind limb preparation confirmed that the sympatholytic effect of prazosin occurred within the limb itself.     

Plasma lipids in genetically hypertensive rats of the Lyon strain

Of the four standardized strains of genetically hypertensive rats, only the Lyon hypertensive rats spontaneously exhibit a higher body weight than their normotensive controls. In order to determine if this increased body weight is associated with alterations in the lipid metabolism, plasma triglycerides (TG), phospholipids (PL), total cholesterol (TPC), and high-density lipoprotein cholesterol (CHDL) were followed in Lyon hypertensive (LH), normotensive (LN), and hypotensive (LL) male rats between 5 and 32 weeks of age. TG were stable with age in LL and LN but increased in LH rats. PL decreased in LL, remained stable in LN, but increased with age in LH rats. TPC and CHDL were stable in LL and LN and increased with age in LH rats. Plasma lipids were not related to the blood pressure level, but were positively related to the body weight in the hypertensive strain. Thus, starting at the age of 5 weeks, LH rats exhibit spontaneously a significant increase in blood pressure, body weight, and plasma lipid concentrations.     

Prenatal influence of substance P on blood pressure and stress sensitivity of spontaneously hypertensive rats

Substance P, administered i.p. to female spontaneously hypertensive rats in the last 6 d of gestation, diminishes the age dependent increase of blood pressure especially in male offspring and the additionally stress related blood pressure increase in both sexes.     

Prominent depressor response to endothelin in spontaneously hypertensive rats

Administration of endothelin (0.03-3.0 micrograms/kg i.v.) caused transient depressor responses followed by sustained pressor responses in anesthetized spontaneously hypertensive rats (SHR) and normotensive Wistar-Kyoto rats (WKY). The initial depressor response occurred at lower doses (0.1 versus 0.3 micrograms/kg i.v.) in SHR versus WKY. The secondary pressor response was attenuated in SHR compared to WKY in both the threshold dose (3.0 versus 0.1 microgram/kg i.v.) and maximum effect at high doses (52 versus 91% at 3.0 micrograms/kg i.v.). In conscious SHR and WKY, endothelin elicited comparable initial depressor responses with increases in heart rate; the secondary pressor responses were attenuated compared to those in anesthetized rats. Therefore endothelin elicits a prominent depressor response, which may be associated with afterload reduction, in SHR.     

Role of eicosanoids in PAF-induced increases of the vascular permeability in rat airways.

1. Platelet activating factor (PAF; 1.0 and 5.0 micrograms kg-1) injected in the tail vein of unanaesthetized rats dose-dependently increased the vascular permeability of the trachea, upper and lower bronchi (up to 400%) as measured by the extravasation of Evans blue dye. The permeability of the parenchyma was not affected by PAF treatment. 2. Pretreatment of the animals with an intravenous injection of the PAF antagonist BN-52021 (10 mg kg-1) abolished almost totally the vascular permeability changes elicited by PAF injection (5.0 micrograms kg-1). 3. Pretreatment of the animals with intravenous injections of inhibitors of thromboxane formation, indomethacin (10 mg kg-1) and compound OKY-046 (10 mg kg-1), and thromboxane antagonist, compound L-655,240 (5 mg kg-1), partially reduced PAF effects in the airways (from 28 to 69%). The thromboxane mimic U-44069 (5.0 micrograms kg-1) did not modify the vascular permeability of rat airways. The effect of a low dose of PAF (0.1 microgram kg-1) on the vascular permeability of the trachea and bronchi (but not of the parenchyma) was potentiated by compound U-44069 (5.0 micrograms kg-1) or noradrenaline (400 ng kg-1) whereas the effect of a high dose of PAF (5.0 micrograms kg-1) was not affected. 4. Neither the peptidoleukotriene antagonist MK-571 (10 mg kg-1) nor the 5-lipoxygenase inhibitor, L-663,536 (10 mg kg-1) given before the injection of PAF (5.0 micrograms kg-1) affected the protein extravasation in rat lung tissues.(ABSTRACT TRUNCATED AT 250 WORDS)