P38 MAPK信号通路在漆树酸改善苯肾上腺素诱导的小鼠心肌细胞肥大中的作用

目的:探讨P38丝裂原活化蛋白激酶(P38 mitogen-activated protein kinase,P38 MAPK)信号通路在漆树酸改善苯肾上腺素(phenylephrine,PE)诱导的小鼠心肌细胞肥大中的作用。方法:原代培养新生小鼠心肌细胞,PE诱导心肌细胞肥大。按随机数字表法将细胞分为空白对照组、溶剂对照组、PE组、PE+漆树酸组、PE+漆树酸+P38抑制剂组和PE+P38抑制剂组。收集干预48 h后的乳鼠心肌细胞进行以下检测:Western blot检测p-P38、第9位赖氨酸乙酰化的组蛋白H3(acetylated histone H3 at lysine 9,H3K9ac)和心房钠尿肽(atrial natriuretic peptide,ANP)的蛋白表达水平,免疫共沉淀(co-immunoprecipitation,Co-IP)法验证p-P38与H3K9ac蛋白之间的相互作用,RT-qPCR检测肌细胞增强因子2C(myocyte enhancer factor 2C,MEF2C)mRNA表达水平,免疫荧光染色观察小鼠心肌细胞表面积。结果:Western blot及RT-qPCR结果表明小鼠心肌细胞中p-P38和H3K9ac水平在PE组显著高于空白对照组(P<0.05),心脏核心转录因子MEF2C及心肌肥厚标志物ANP表达水平在PE组显著高于空白对照组(P<0.05);而在PE处理的心肌细胞中,P38抑制剂和漆树酸能够显著降低p-P38和H3K9ac水平,且MEF2C转录水平及ANP蛋白表达水平在PE+P38抑制剂组和PE+漆树酸组也较PE组显著降低(P<0.05);Co-IP结果表明p-P38与H3K9ac存在相互调控关系;免疫荧光结果表明,与空白对照组相比,PE组心肌细胞表面积显著增大(P<0.05),而P38抑制剂和漆树酸干预后能显著降低PE诱导的心肌细胞肥大(P<0.05)。结论:漆树酸能改善PE诱导的心肌细胞肥大,其作用机制可能与调节P38 MAPK信号通路介导的组蛋白乙酰化修饰失衡有关。     

神经降压素和新福林对大鼠下丘脑减压区神经元放电的影响

观察了升压以及离子微电泳神经降压素(NT),微量注射抗NT 血清对大鼠下丘脑减压区(HDA)神经元放电的影响。结果表明,多数HDA 神经元对升压呈兴奋性反应;HDA 区微量注入抗NT 血清后,这一反应受到抑制;微电泳NT 可兴奋部分HDA 神经元,主要是对升压呈兴奋性反应的神经元。提示HDA 区可能是减压反射中枢通路的组成部分,NT 可能作为调制物起作用。     

Increased sensitivity to α-adrenoceptor stimulation but intact purinergic and muscarinergic effects in prehypertensive cardiac hypertrophy of spontaneously hypertensive rats

Summary The effects of phenylephrine, isoprenaline and adenosine, (–)-N⁶-phenylisopropyladenosine (PIA) or carbachol alone and in the presence of isoprenaline on force of contraction were studied in isolated electrically driven papillary muscles of spontaneously hypertensive rats (SHR) and age-matched Wistar control rats. In SHR an increased heart to body weight ratio was observed when blood pressure was not yet elevated. During this stage of the syndrome (i.e. between the 27th and 35th day of life) phenylephrine was about 3.4 times more potent to increase force of contraction in SHR (mean EC₅₀: 2.8 mol l^–1) than in control rats (mean EC₅₀: 9.4 mol l^–1). The positive inotropic effect of isoprenaline was similar in SHR and control rats. Also no difference could be detected in the isoprenaline-antagonistic effect of adenosine, the adenosine receptor agonist PIA or carbachol. We conclude that an increased sensitivity to cardiac -adrenoceptor stimulation might be related to prehypertensive cardiac hypertrophy in SHR.     

Electrophysiologic and inotropic effects of α-adrenoceptor stimulation in human isolated atrial heart muscle

Summary The effects of -adrenoceptor stimulation on force of contraction were investigated in human atrial heart muscle and compared with those of -adrenoceptor stimulation. The maximal positive inotropic effect produced by stimulation of -adrenoceptors with phenylephrine (in the presence of atenolol 10 mol/l) was significantly smaller than that seen in response to -adrenoceptor stimulation with isoprenaline. The maximal effect of phenylephrine (25% of the maximal effect of isoprenaline) required far higher concentrations (1 mmol/l) than isoprenaline (100 nmol/l); the EC₅₀ values amounted to 33.1 mol/l and 3.3 nmol/l, respectively. In the presence of the -adrenoceptor blocking agent phentolamine (1 mol/l), the concentration-response curve of phenylephrine was displaced to higher concentrations of the agonist; under these conditions, the EC₅₀ value amounted to 52.5 mol/l, The effects of the catecholamines noradrenaline and adrenaline on force of contraction remained unchanged in the presence of phentolamine (1 mol/l), or prazosin (1 mol/l), The positive inotropic effect of phenylephrine (1 mmol/l) was associated with a slight decrease in action potential duration; the effects on action potential were completely blocked in the presence of phentolamine (1 mol/l) These findings support the view that selective stimulation of -adrenoceptors may mediate a small but detectable positive inotropic effect in human atrial tissue under in vitro conditions. The requirement of high concentrations of -adrenoceptor agonists and the lack of effects of the endogenous catecholamines adrenaline and noradrenaline on -adrenoceptors (in concentrations which fully elicit the -adrenoceptors-mediated response) do not provide a basis for a functional role of -adrenoceptor-mediated effects under in vivo conditions. It is more likely that adrenaline- or noradrenaline-mediated changes in the force of contraction in the human atrium are virtually exclusively due to the stimulation of -adrenoceptors. Send offprint requests to H. Nawrath at the above address     

Contribution of both α- and β-adrenoceptors to the inotropic effects of catecholamines in the rabbit heart

Summary The functional role of -adrenoceptors was investigated in different parts of the rabbit heart. Phenylephrine (PE) caused a marked increase in force of contraction (F_c) and a prolongation of the action potential (AP) in preparations from the left atrium and the right ventricle. The response was less pronounced in the right atrium and in the left ventricle, whereas APs of spontaneously beating sinoatrial preparations remained completely unchanged. Phentolamine as well as the diesters phorbol 12,13 dibutyrate (PDBu) or 12-O-tetradecanoylphorbol-13-acetate (TPA) eliminated the effects of PE. The contribution of a-adrenoceptors to the effects of adrenaline (Adr) and noradrenaline (NA) on F_c was determined in preparations from the right ventricle. Phentolamine and the phorbol diesters reduced the effects of Adr and NA by about 30 to 60%; the remaining response was abolished by propranolol. It can be derived from our experiments that, in some parts of the rabbit heart, a considerable amount of the effects of Adr and NA is due to the stimulation of a-adrenoceptors. The present findings therefore support the view that, in the rabbit heart, the maximally effective drive of the heart requires the stimulation of both - and -adrenoceptors. The inhibitory effects of phorbol diesters on the -adrenoceptor-mediated response indicate that the activation of protein kinase C (PKC) specifically uncouples -adrenoceptors from the effector system, whereas the response to -adrenoceptor stimulation remains unchanged.Correspondence to: H. Nawrath at the above address     

山莨菪碱对离体血管和心房细胞内、外钙影响的研究

山莨菪碱(Ani)能拮抗PE和高K~+所致兔主动脉条收缩,IC_(50)分别为120和86μmol/L,两者比值PE/K~+(IC_(50))=1.39,小于Ver;对5-HT两种收缩成分均有抑制作用;亦能抑制豚鼠左房“静息后增强”和“阶梯现象”;对CaCl_2收缩兔主动脉和豚鼠左房具有非竞争性抑制作用。结果提示,山莨菪碱对细胞外钙经PDC和ROC所致收缩以及由细胞内钙释放诱导的收缩均有拮抗作用。     

An open-label randomized controlled clinical trial for comparison of continuous phenylephrine versus norepinephrine infusion in prevention of spinal hypotension during cesarean delivery

BackgroundDuring spinal anesthesia for cesarean delivery phenylephrine is the vasopressor of choice but can cause bradycardia. Norepinephrine has both β- and α-adrenergic activity suitable for maintaining blood pressure with less bradycardia. We hypothesized that norepinephrine would be superior to phenylephrine, requiring fewer rescue bolus interventions to maintain blood pressure.MethodsEighty-five parturients having spinal anesthesia for elective cesarean delivery were randomized to Group P (phenylephrine 0.1 μg/kg/min) or Group N (norepinephrine 0.05 μg/kg/min) fixed-rate infusions. Rescue bolus interventions of phenylephrine 100 μg for hypotension, or ephedrine 5 mg for bradycardia with hypotension, were given as required to maintain systolic blood pressure. Maternal hemodynamic variables were measured non-invasively.ResultsThere was no difference between groups in the proportion of patients who required rescue vasopressor boluses (Group P: 65.8% [n=25] vs. Group N: 48.8% [n=21], P=0.12). The proportion of patients who received ⩾1 bolus of phenylephrine was similar between groups (Group P: 52.6% [n=20] vs. Group N: 46.5% [n=20], P=0.58). However, more patients received ⩾1 bolus of ephedrine in the phenylephrine group (Group P: 23.7% [n=9] vs. Group N: 2.3% [n=1], P <0.01). The incidence of emesis was greater in the phenylephrine group (Group P: 26.3% vs. Group P: 16.3%, P <0.001). Hemodynamic parameters including heart rate, the incidence of bradycardia, blood pressure, cardiac output, cardiac index, stroke volume, and systemic vascular resistance and neonatal outcome were similar between groups (all P <0.05).ConclusionNorepinephrine fixed-rate infusion has efficacy for preventing hypotension and can be considered as an alternative to phenylephrine.     

The inhibition of α1-adrenoceptor-mediated contractions of rabbit pulmonary artery by Ca2+-withdrawal,pertussis toxin and N-ethylmaleimide is dependent on agonist intrinsic efficacy

Summary Contractions were induced in rings of rabbit pulmonary artery with the preferential ₁-adrenoceptor agonists, whereas St 587, clonidine and B-HT 920 were (parchloro-trifluoromethyl-phenylimino)[imidazolidine] and the preferential ₂-adrenoceptor agonists, clonidine and B-HT 920 [6-allyl-2-amino-5,6,7,8-tetrahydro-4H-thiazolo-(4,5-d) azepine]. Phenylephrine and methoxamine acted as full agonists whereas St 587, clonidine and B-HT 920 were partial agonists (intrinsic activities 0.62, 0.38 and 0.42, respectively). Experiments with ₁- and ₂-adrenoceptor antagonists indicated that the receptors involved are of the ₁ type only. Removal of extracellular Ca²⁺ inhibited maximal contractions to phenylephrine and methoxamine by 30% and 49%, respectively. The remaining contraction components of the full agonists were abolished by the intracellular Ca²⁺ antagonist TMB-8 [8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate]. Contractions to St 587, clonidine and B-HT 920 were virtually abolished in Ca²⁺-free medium. Pretreatment of the donor rabbits with pertussis toxin (2.5 /kg i. v., 5–6 days before sacrifice) attenuated the efficacies of the full agonists, phenylephrine and methoxamine by only 24% and 17%, respectively, whereas maximal contractions to the partial agonists, St 587, clonidine and B-HT 920, were inhibited by 46%, 61% and 75%, respectively. Also the sulfhydryl reagent, N-ethylmaleimide (10 M), reduced contractile efficacies of phenylephrine and methoxamine to a lesser degree than those of St 587, clonidine and B-HT 920. When agonists were used at equieffective concentrations (i.e. EC_30–40 for phenylephrine and methoxamine, EC_70–80 for St 587 and EC₉₉ for clonidine and B-HT 920) the degree of inhibition by removal of extracellular Ca²⁺, pertussis toxin and N-ethylmaleimide was similar for all agonists. These data suggest that a unitary al-receptor may stimulate contractions via two different mechanisms. At a low degree of receptor stimulation, contractions are mediated by a pertussis toxin- and N-ethylmaleimide-sensitive influx of external Ca²⁺. At a higher degree of receptor stimulation, an additional mechanism is activated which is insensitive to the two G protein inhibitors and mediated by Ca²⁺ mobilization from intracellular sites.A preliminary account of these results was presented at the Fall Meeting of the German Society of Pharmacology and Toxicology, Hamburg, September 19–22,1988 (Liebau et al. 1988). The study was supported by Grant Fo 144/1–2 from the Deutsche Forschungsgemeinschaft     

Typical and atypical neuroleptics are potent antagonists at α1-adrenoceptors of the dorsal lateral geniculate nucleus

Summary The present electrophysiological studies examined the actions of neuroleptics at central ₁adrenoceptors in the rat. In single-cell recording experiments, typical and atypical neuroleptics, when administered systemically or locally (iontophoresis and pressure ejection), were found to be potent antagonists of activating ₁adrenoceptor responses in the dorsal lateral geniculate nucleus (dLGN). Doses of neuroleptics effective as antagonists at ₁adrenoceptors had very weak effects as muscarinic receptors in the dLGN. Since doses of neuroleptics employed in the present study were within the clinical range, it appears likely that central ₁adrenoceptors would be blocked during neuroleptic therapy in humans.     

The effects of alaproclate on the pupillary responses to tyramine,phenylephrine and pilocarpine in depressed patients

Nine depressed patients were treated with alaproclate, a selective 5-HT uptake inhibitor, for 3 weeks in a dose of 400 mg daily. The pupillary responses to tyramine, phenylephrine, and pilocarpine eye drops were measured on consecutive days before, after 1 week and after 3 weeks of treatment. The tyramine-induced mydriasis was unaffected by alaproclate, suggesting that it does not significantly inhibit the reuptake of noradrenaline. The pilocarpine-induced miosis and the phenylephrine-induced mydriasis were both enhanced after 1 week but not after 3 weeks of treatment. This suggests that alaproclate acutely increases the responsiveness of postsynaptic muscarinic and ₁ adrenoceptors.