脑室内注入TRH对大鼠肝脏无机磷代谢影响的核磁共振分析

采用在大鼠脑室内注入促甲状腺激素释放激素（ＴＲＨ）,并利用＾３１Ｐ－核磁共振法测定活体大鼠肝脏中的含磷化学物质,并观察ＴＲＨ对肝脏无机磷代谢的影响。研究证明,ＴＲＨ通过中枢神经影响肝脏中无机磷的代谢,由侧脑室注入ＴＲＨ,使肝脏无机磷含量发生显著增加,此作用由于副交感神经的阻断剂阿托品的加入而消失,由此可以认为,ＴＲＨ是经由副交感神经而影响肝脏的代谢。     

脑室内注入TRH对大鼠肝胆生化影响机理的研究

在大鼠的脑室内注入ＴＲＨ（三肽酰胺）,观察其对大鼠肝胆汁分泌的影响．实验结果表明,侧脑室内注入ＴＲＨ对胆汁分泌量有明显的增强作用,并且随ＴＲＨ剂量加大其作用逐渐增强．而且在侧脑室内注入ＴＲＨ期间,胆汁中Ｋ＋、Ｃｌ－、Ｎａ＋、ＨＣＯ３－离子的排出量亦有增加．其机理在于,侧脑室内注入ＴＲＨ,激活中枢胆碱能系统,并通过送走神经而使肝的新陈代谢发生变化．     

败血症休克大鼠肝脏内质网钙ATP酶磷酸化及去磷酸化的改变

本文观察了早期、晚期败血症休克大鼠肝脏内质网钙ＡＴＰ酶磷酸化的改变。败血症休克模型由结忾大鼠盲肠并穿孔的方法复制。采用蔗糖密度梯度离心法分离肝脏内质网。由聚丙烯酰胺凝胶电泳鉴定肝脏内质网钙ＡＴＰ酶磷酶化中间产物。     

克伦特罗对大鼠肝脏氮代谢及IGF-I水平的影响

目的探讨克伦特罗(CL)影响机体物质代谢的有关肝脏机制.方法利用大鼠离体肝脏灌流技术测定CL对肝脏灌流液中尿素氮水平,肝组织谷丙转氨酶(GPT)活性以及肝脏胰岛素样生长因子I(IGF-I)合成和分泌的影响.结果CL可使大鼠离体肝脏产生的尿素氮浓度下降,并有一定的剂量效应和时间效应.在给药后灌流的1、2、3、4h内1×10-6 mol/L的CL使大鼠肝脏产生的尿素氮分别下降15.02% (P>0.05)、17.97% (P>0.05)、26.76%(P<0.05)和30.08%(P<0.01),1×10-8mol/L的CL具有类似的效应.CL抑制大鼠肝组织中GPT的活性,×10-6mol/L的CL使得肝组织中GPT活性下降24.65%(P<0.05).CL还影响大鼠离体肝脏IGF-I的生成和分泌,×10-6 mol/L CL使大鼠肝组织内IGF-I的含量比对照组升高19.77%(P<0.05),灌流液中IGF-I的水平也呈增加的趋势.结论CL可通过增加对肝脏氮的储留及增强肝脏IGF-1的合成和分泌而促进机体的物质代谢.     

大鼠实验性急性肝衰竭时微量元素铁,铜,锌及其结合蛋白质的变化

肝脏是微量元素代谢的重要器官。肝功能的紊乱,会导致微量元素的代谢异常。关于急性肝衰竭肝脏和脑组织微量元素代谢的研究国内外报道很少。尤其是关于微量元素及其结合蛋白的代谢,国内未见报导。如果单研究微量元素而不研究其结合蛋白质的代谢,这种研究是不全面的。为此,我们观察了大鼠实验性急性肝衰竭时,血清、肝脏、脑组织铁、铜、锌及血清中相应结合蛋白质的变化。     

应激对同型半胱氨酸代谢的负性调节

基于应激对高同型半胱氨酸血症具有诱导作用,本文探索了应激致同型半胱氨酸(homocysteine,HCY)代谢变化的关键环节,并初步揭示了该作用的意义。以束缚应激法建立大鼠应激模型,采用高压液相-荧光检测法测定血浆HCY水平,用放射性酶学法检测不同组织中胱硫醚β合成酶(cystathionine beta-synthase,CBS)活性的变化,以及RT-PCR法和Northern blot法检测CBS mRNA水平的变化。结果可见,束缚应激可导致大鼠高同型半胱氨酸血症的发生;CBS在肝脏具有最强的代谢活性,肾脏其次,而心脏和血液中活性极低;应激大鼠肝脏CBS活性和mRNA水平均显著降低(P<0.05),应激3周时分别为对照组的70.6％±5.9％和55.9％±4.3％。以上研究结果表明,应激对HCY转硫代谢途径存在负性调节作用,其对肝脏CBS基因转录水平的调控是应激所致高同型半胱氨酸血症发生的重要诱因;肝脏是应激对HCY代谢调节的主要场所。     

茶多酚对营养性肥胖大鼠肝脏自由基代谢的影响

目的:探讨茶多酚对营养性肥胖大鼠肝脏自由基代谢的影响。方法:采用高脂饲料喂养,体重(200±20)g的雄性SD大鼠32只,随机分为4组(n=8),测定各组大鼠肝脏细胞O自由基和N自由基。结果:高脂饲料组大鼠肝脏超氧化物歧化酶(SOD)、过氧化氢酶(CAT)活性显著提高,茶多酚补充组丙二醛(MDA)含量比对照组及高脂饲料组显著下降;高脂饲料组大鼠肝脏TNOS、iNOS活性及NO含量显著升高,茶多酚降低了总-氧化氮合酶(TNOS)、诱导型一氧化氮合酶(iNOS)活性及NO含量。结论:高脂饲料诱导了大鼠肝脏细胞的氧化应激状态,茶多酚提高了营养性肥胖大鼠肝脏的抗氧化能力,对营养性肥胖大鼠肝脏有一定的保护作用。     

烧伤大鼠常规营养物质代谢的变化

选取体重为200g左右的健康雄性普通级Wistar大鼠20只,随机分为烧伤组和对照组,分别单饲于大鼠代谢笼中,研究烧伤大鼠常规营养物质代谢的变化情况。实验结果表明烧伤不同程度地降低(P＜0.01或0.05)大鼠的采食量、排粪量、排尿量以及粪中蛋白质、粗脂肪和钙、磷的含量,而提高(P＜0.01或0.05)饲料中蛋白质、粗脂肪和钙、磷的消化率以及尿中氮的含量,烧伤后最初3天这种变化更为明显,体现了大鼠在烧伤应激状态下的代谢补偿作用和烧伤后的高分解代谢反应。     

无机磷对力复霉素合成的调节

本文报道无机磷抑制力复霉素产生菌地中海诺卡氏菌U-32中力复霉素(SV)的合成。随着丰富培养基中无机磷浓度的增加,SV的合成受到明显抑制,最高抑制率达sO％,而阔体生长则增加65％。不同时间加入无机磷对抗生素产量的影响是不相同的,在抗生素合成前(O一48h),无机磷的加入能严重影响SV的合成,但在合成期(72 h以后)加入则几乎不影响SV的产量。提高培养基中无机磷的起始浓度,使菌体合成脂肪量增加70％：甲基丙二酰CoA羧基转移酶和甲基丙二酰CoA羧基变位酶的活力受到明显抑制：菌体内腺苷化台物ADP、ATP的含量在整个发酵期都明显增加,细晦内能荷水平也因培养基中无机磷的起始浓度增加而提 高。     

非诺贝特对衰老大鼠肝脏组织肉毒碱棕榈酰转运酶Ⅰ水平的影响

目的:观察非诺贝特对衰老大鼠肝脏组织肉毒碱棕榈酰转运酶Ⅰ水平的影响,从而探讨衰老过程中出现脂质代谢异常的可能机制及非诺贝特对脂质代谢的调节作用.方法:雄性SD年轻大鼠(4～6周龄)16只和老年大鼠(24个月龄)16只,分别随机分为对照组和非诺贝特组(非诺贝特喂养2周),测定大鼠血清中三酰甘油和总胆固醇水平,采用半定量逆转录聚合酶链反应法检测大鼠肝脏组织肉毒碱棕榈酰转运酶Ⅰ水平.结果:年轻对照组比较,老年对照组的三酰甘油和总胆固醇水平升高,大鼠肝脏组织肉毒碱棕榈酰转运酶Ⅰ水平表达降低.非诺贝特组与老年对照组比较三酰甘油和总胆固醇水平均下降,非诺贝特升高不同年龄组大鼠肝脏组织肉毒碱棕榈酰转运酶Ⅰ水平.结论:衰老过程中大鼠肝脏组织肉毒碱棕榈酰转运酶Ⅰ水平表达减少可能与老年脂质代谢异常有关.     

Control of glucose balance in the perfused rat liver by the parasympathetic innervation

Electrical stimulation of the nerve bundles around the hepatic artery and the portal vein activates both the sympathetic and parasympathetic liver nerves; the sympathetic effects clearly predominate. Parasympathetic effects were therefore studied in the rat liver perfused in situ by perivascular nerve stimulation in the presence of both an alpha- and a beta-blocker. In the presence of the alpha-blocker phentolamine and the beta-blocker propranolol all sympathetic nerve effects were prevented; the remaining parasympathetic stimulation had no influence on the basal glucose and lactate metabolism nor on the hemodynamics. Insulin alone, with both alpha- and beta-blockade, provoked a small, parasympathetic nerve stimulation in the presence of insulin a more pronounced enhancement of glucose utilization. In the presence of an alpha- and beta-blocker perivascular nerve stimulation antagonized the glucagon stimulated glucose release, but did not affect lactate exchange. The nerve effect was abolished by the parasympathetic antagonist atropine. Acetylcholine or insulin, with both an alpha- and beta-blocker present, mimicked the effects of nerve stimulation antagonizing the glucagon-stimulated glucose release. Nerve stimulation in the presence of insulin was more effective than either stimulus alone. The present results show that in rat liver stimulation of the parasympathetic hepatic nerves has direct effects on glucose metabolism synergistic with insulin and antagonistic to glucagon.     

Involvement of the autonomic nervous system in the in vivo TRH-induced increases in the plasma levels of glucagon, insulin and glucose in rabbits

Thyrotropin-releasing hormone, TRH, increases the plasma levels of glucagon, insulin, glucose and free fatty acids in rabbits. However, TRH has no direct effects on the release of hormones neither from the endocrine pancreas in humans nor from the isolated perfused rat pancreas. The aim of the present study was to investigate if the effects of TRH in rabbits were mediated by the autonomic nervous system. The TRH "Roche"-induced hyperglucagonemia was inhibited by phentolamine (an alpha-receptor blocking drug), yohimbine (an alpha-2 -receptor blocking drug) and atropine. The TRH "Roche"-induced hyperinsulinemia was inhibited by propranolol (a beta-receptor blocking drug). The TRH "Roche"-induced hyperglycemia was inhibited by all four drugs. The TRH "Roche"-induced increases in the plasma levels of free fatty acids were not inhibited by the sympathetic and parasympathetic blocking drugs. The effects of TRH "Roche" on the plasma levels of glucagon, insulin and glucose cannot be explained by increases in the plasma levels of catecholamines. TRH, given intravenously into rabbits, may possibly act on regions in the central nervous system which control carbohydrate metabolism and the release of glucagon and insulin from the endocrine pancreas by sympathetic and parasympathetic mechanisms.     

Electron-microscopic cytochemistry of the catecholaminergic innervation of TRH neurons in the rat hypothalamus

Summary The catecholaminergic innervation of thyrotropin-releasing hormone (TRH) neurons was examined by use of a combined method of 5-hydroxydopamine (5-OHDA) uptake or autoradiography after intraventricular injection of ³H-noradrenaline (³H-NA) and immunocytochemistry for TRH in the same tissue sections at the electron-microscopic level.TRH-like immunoreactive nerve cell bodies were distributed abundantly in the parvocellular part of the paraventricular nucleus (PVN), in the suprachiasmatic preoptic nucleus and in the dorsomedial nucleus of the rat hypothalamus. In the PVN, a large number of immunonegative axon terminals were found to make synaptic contact with TRH-like immunoreactive cell bodies and fibers. In the combined autoradiography or 5-OHDA labeling with immunocytochemistry, axon terminals labeled with ³H-NA or 5-OHDA were found to form synaptic contacts with the TRH immunoreactive nerve cell bodies and fibers. These findings suggest that catecholamine-containing neurons, probably noradrenergic, may innervate TRH neurons to regulate TRH secretion via synapses with other unknown neurons in the rat PVN.This study was supported by grants from the Ministry of Education, Science and Culture, Japan     

The degradation of intravenously injected chondroitin 4-sulphate in the rat

The degradation of chondroitin 4-[(35)S]sulphate isolated from chick-embryo cartilage was studied in the rat by experiments on free-range animals, on wholly anaesthetized animals with ureter cannulae, by perfusion of isolated liver, by whole-body radioautography and by isolation of liver lysosomes. After injection into rats 68% of the radioactivity was recovered in the urine after 24h, approximately one-half of this being in the form of low-molecular-weight material, chiefly inorganic sulphate. Cannulation experiments demonstrated that the proportion of low-molecular-weight components excreted in the urine increased with time until, after 12h, virtually all was inorganic sulphate. Whole-body radioautography identified the liver as the major site of radioisotope accumulation after injection of labelled polysaccharide. Perfusion through isolated liver indicated that this organ has the ability to metabolize the polymer with the release of low-molecular-weight products, principally inorganic sulphate. Incubation of a lysosomal fraction prepared from rat liver after injection of chondroitin 4-[(35)S]sulphate gave rise to degradation products of low molecular weight, and experiments in vitro with rat liver lysosomes confirmed that these organelles are capable of the entire degradative process from chondroitin sulphate to free inorganic sulphate.     

Effect of etimizol on energy metabolism in rat brain]

Intraperitoneal injection of ethimizol in a dose of 25 mg/kg caused in intensification of the oxidative phosphorylion, an increase in creatine phosphate and a reduction of inorganic phosphorus concentration in the tissue of the rat brain. It is supposed that stimulation of the energy metabolism by ethimizol was caused by its activating effect on adenyylcyclase.     

Increase of tonic parasympathetic outflow to the pupil produced by an analog of TRH (MK-771)

MK-771, a potent analog of thyrotropin-releasing, hormone, was found to cause a long-lasting, dose-dependent antagonism of the centrally induced pupillary dilation produced by clonidine in anesthetized cats. MK-771 had little direct effect on the dilated iris in cats treated with mecamylamine. Both MK-771 and TRH selectively antagonized the pupillary dilation, but not the contractions of the nicitating membrane induced by peripheral sympathetic nerve stimulation. MK-771 was found to increase nerve activity in the short ciliary nerve. TRH, although studied less extensively, produced similar effects. This action of MK-771 was not blocked by prior sectioning of the spinal cord, by elimination of the tonic light reflex pathway, or by treatment with scopolamine or atropine. These findings suggest that the pupillary effects of MK-771 (and TRH) are related to the ability to increase the parasympathetic tone to the iris.     

Stimulation by thyrotropin-releasing hormone of vagal outflow to the thyroid gland

An intracerebroventricular (i.c.v.) injection of TRH to the urethane anesthetized rat stimulates the activity of the superior laryngeal nerve (n.sl) which is a vagal ramus terminating at the thyroid gland and adjacent muscles. The response to TRH, a tonic increase in the n.sl outflow, was dose dependent in the 0.005-5.0 micrograms/100 g B.W. range. In contrast to this, methionine-enkephalin (ENK), neurotensin (NT) and somatostatin (SRIF) (5 micrograms/100 g, i.c.v.) all caused a transient decrease in n.sl activity. SRIF showed the highest attenuating effect when injected alone and was capable of diminishing the increased activity produced by a prior injection of TRH. ENK and NT failed to affect the TRH-induced increased activity. When injected concomitantly with TRH, SRIF blocked the response to TRH while ENK and NT both failed to affect the response to TRH. Pretreatment with triiodothyronine for 5 days strongly inhibited the response of the n.sl outflow to TRH. On the other hand, pretreatment with atropine, haloperidol, propranolol, phenoxybenzamine and p-chlorophenylalanine failed to block the stimulating effect of TRH although the response was diminished by some antagonists. It therefore seemed that TRH transmission is involved in central stimulation and SRIF is antagonistic in this regulation of n.sl outflow to the thyroid gland.     

Neuropeptides as central integrators of autonomic nerve activity: effects of TRH, SRIF, VIP and bombesin on gastric and adrenal nerves

The nerve activity of the gastric ramus of the splanchnic (sympathetic) nerve, gastric ramus of the vagus, adrenal ramus of the splanchnic nerve and the superior laryngeal nerve (laryngeal ramus of vagus) were assessed before and after i.c.v. injection of neuropeptides in the rat. TRH stimulated the vagal branch but attenuated the sympathetic outflow to the stomach. In contrast, the sympathetic outflow to the adrenal was enhanced by TRH. SRIF suppressed the activity of all the nerves studied. VIP did not affect the sympathetic outflow to the stomach while suppressing the gastric branch of the vagus. The adrenal sympathetic branch as well as the superior laryngeal nerve was stimulated by VIP. Bombesin suppressed both vagal and sympathetic outflow to the stomach but markedly stimulated the laryngeal branch of the vagus. The adrenal sympathetic nerve was either stimulated or attenuated slightly by bombesin. These results indicate that centrally administered neuropeptides produce reactions specific for each nerve.     

Parasympathetic cholinergic vasodilator mechanism in the terminal liver microcirculation in rats.

Changes in the diameter of liver sinusoids were studied by an intravital television microscope method in pentobarbital-anaesthetized rats. Dilatation of liver sinusoids was observed during parasympathetic neural stimulation and during acetylcholine administration. Frequency-dependent stimulation-effect relationships were obtained by electrical excitation of intact vagus nerves at supramaximal intensity from 2 to 8 Hz. Acetylcholine concentration-effect relationships were also obtained by intraportal venous infusions of acetylcholine 30 microliter for 5 s from 10(-9) to 10(-2) mol.1(-1). Systemic cholinergic receptor blockade with atropine (1 mg.kg-1) markedly reduced dilatation of liver sinusoids produced by both vagus nerve stimulation and acetylcholine administration. Changes in diameter of liver sinusoids with frequency of neural stimulation and with concentration of administered acetylcholine were also expressed as percentage of observed maximum effect and the respective stimulation-effect curves were constructed such that at a certain percentage of diameter change, the equivalent level of vagus nerve activity was represented by a given concentration of administered acetylcholine. Liver plasma concentration of acetylcholine presumably released during electrical vagal stimulation and reaching liver sinusoids was also estimated and found to be within physiological range. It is therefore proposed that rat liver sinusoids have the capacity for parasympathetic cholinergic vasodilatation.     

Ultrastructural relationship between monoamine- and TRH-containing axons in the rat median eminence as revealed by combined autoradiography and immunocytochemistry in the same tissue section

Summary The correlation of dopamine (DA)-, noradrenaline (NA)- or serotonin (5HT)-containing neurons and thyrotropin releasing hormone (TRH)-containing neurons in the median eminence of the rat, as well as the coexistence of monoamines (MA) and TRH in the neurons, were examined by subjecting ultrathin sections to a technique that combines MA autoradiography and TRH immunocytochemistry. The distribution and localization of silver grains after ³H-MA injection were examined by application of circle analysis on the autoradiographs.TRH-like immunoreactive nerve terminals containing the immunoreactive dense granular vesicles were found to have an intimate contact with monoaminergic terminals labeled after ³H-DA, ³H-NA or ³H-5HT infusion in the vicinity of the primary portal capillaries in the median eminence. Synapses between TRH-like immunoreactive axons and MA axons labeled with silver grains, however, have not been observed to date. Findings suggesting the coexistence of TRH and MA in the same nerve terminals or the uptake of ³H-MA into TRH-like immunoreactive nerve terminals, where silver grains after ³H-MA injection were concurrently localized in TRH-like immunoreactive nerve terminals, were rarely observed in the median eminence. Percentages of the nerve terminals containing both immunoreactive granular vesicles and silver grains after ³H-MA injection to total nerve terminals labeled after ³H-MA infusion silver grains were equally very low in ³H-DA, ³H-NA or ³H-5HT, amounting to less than 6.1%.This work was supported in part by grant-in-aid for scientific research from the Japan Ministry of Education (No. 557018).