Forskolin-stimulated Adenylate Cyclase Activity in Rat Cerebral Cortex Following Chronic Treatment with Psychotropic Drugs

Abstract: Rats were treated with lithium, imipramine, reserpine, and lithium combined with imipramine or reserpine. Lithium was given in the diet (40 mmol/kg) resulting in a serum-Li⁺ level of 0.5–0.6 mmol/1. Other drugs were dissolved in 0.9% saline and given intraperitoneally once or twice daily. After 3 weeks of treatment, forskolin-stimulated adenylate cyclase activity was measured in cerebral cortex homogenates. Reserpine did not affect the forskolin stimulation, while both imipramine and lithium caused a decrease in this activity. The combined treatments lithium-imipramine and lithium-reserpine also exhibited a clear decrease in forskolin stimulation, but the effect of concomitant lithium and imipramine treatment did not differ from the effect seen after any of the treatments alone. The unstimulated activity was unaltered by all treatments. The inhibition of lithium and imipramine on the forskolin stimulation indicates an interference of these two drugs with the forskolin-mediated activation of the adenylate cyclase.     

Adrenergic Subsensitivity of a Cell-free Adenylate Cyclase from Rat Brain after Chronic Imipramine Treatment

A particulate adenylate cyclase was prepared from cerebral cortex of rats which had been chronically treated with imipramine. Noradrenaline stimulated adenylate cyclase activity was significantly reduced compared to untreated controls. Neither total phosphodiesterase activity nor basal and maximal adenylate cyclase activity were altered by the imipramine treatment. This indicates the development of adrenoceptor subsensitivity which is functionally retained in the cell-free enzyme preparation.     

Adenylate Cyclase in Rat Synaptosomal Plasma Membranes and Caudate Nucleus Homogenate: Effects of Dopamine,E Prostaglandins,Guanyl-5′-yl-imidodiphosphate and Morphine

Abstract: The adenylate cyclase in two particulate preparations from rat brain, a homogenate from caudate nucleus (CN-homogenate) and a synaptosomal plasma membrane fraction (SPM-fraction) from whole rat brain was investigated. Stimulation of the enzyme by dopamine and prostaglandins E₁ and E₂ was found in the CN-homogenate while only a weak prostaglandin E₁ and E₂ stimulation and no dopamine stimulation could be found in the SPM-fraction. Guanyl-5′-yl-imidophosphate (GppNHp) and NaF could stimulate the adenylate cyclase in both preparations. Morphine up to 10^–5 M altered neither the basal enzyme activity nor any of the stimulated enzyme activities.     

On the Mechanism of Inhibition of Rat Fat Cell Adenylate Cyclase by Lithium

Abstract: This study aimed to elucidate the mechanism by which Li⁺ inhibits adenylate cyclase (AC) in vitro. It was found that Li⁺ inhibited the norepinephrine- (NE) and the fluoride- (F) stimulated AC activities of rat fat cell ghosts at Li⁺ concentrations above 10 mM. The basal enzyme activity was unaffected even at 80 mM of Li⁺. Li⁺ inhibited the NE-induced AC activity in a mainly non-competitive way, but the inhibitory effect decreased with increasing concentrations of NE. The inhibition by Li⁺ of both NE- and F^--stimulated AC activities was antagonized by Mg²⁺. The Mg²⁺ antagonism of the Li⁺-induced inhibition of the NE-stimulated AC activity was independent of the NE concentration. Furthermore, Ca²⁺, inhibiting AC activity by a Mg²⁺ antagonism, abolished the inhibitory effect of Li⁺. It is suggested that Li⁺ affects both the Ka of NE and the Vmax of AC through 1) an inhibitory action of LiATP^3- at the catalytic site of AC or 2) an inhibitory action of Li⁺ at an allosteric Mg²⁺ site of AC.     

Riboflavin: Inhibitory Effects on Receptors, G-Proteins, and Adenylate Cyclase

Riboflavin inhibited binding of both agonist and antagonist radioligands to rat brain A(1)-adenosine receptors with K(i) values of approximately 10 μM. In an adenylate cyclase assay with membrane preparations from either rat adipocytes or DDT MF-2 cells, both of which contain A(1)-adenosine receptors, riboflavin inhibited isoproterenol-stimulated cyclase activity with an IC(50) of approximately 20 μM. However, the inhibition of cyclase by riboflavin was not reversed by an A(1)-selective antagonist, nor by pretreatment with pertussis toxin. Thus, neither A(1)-receptors nor G(i)-proteins appear critically involved in the inhibition of cyclase by riboflavin. Riboflavin did block the stimulation by an adenosine analog of [(35)S]GTPγS binding in rat cerebral cortical membranes. However, riboflavin also inhibited the stimulation by fMLP of [(35)S]GTPγS binding in HL-60 cell membranes. Riboflavin inhibited forskolin-stimulated cyclase in membranes from DDT MF-2 cells > rat adipocytes > PC12 cells, hamster CHO M2 cells, and wild-type S49 cells. There was virtually no inhibition of forskolin-stimulated cyclase in membranes of human platelets, rat cerebral cortex, or cyc(-)S49 cells lacking G(s)-proteins. The calcium-stimulated cyclase in rat cerebral cortical membranes was inhibited by riboflavin. A preincubation of membranes with riboflavin markedly enhanced the inhibition for DDT MF-2 and wild-type and cyc(-)S49 membranes. The extent of inhibition in the different cell lines was dependent on the agent used to stimulate cyclase. Riboflavin, like the P-site inhibitor 2′,5′-dideoxyadenosine, was more potent and efficacious when manganese instead of forskolin was used as the stimulant. However, unlike the P-site inhibitor, riboflavin did not markedly inhibit GppNHp- or fluoride-stimulated cyclase. Riboflavin at low micromolar concentrations appears to have three possibly interrelated effects on second messenger systems subserved by G-proteins. These are antagonism at A(1)-adenosine receptors, inhibition of turnover of guanyl nucleotides at G-proteins, and inhibition of adenylate cyclase.     

鱼油对大鼠心肌细胞膜上β—受体和腺苷酸环化酶活性的影响

本文探讨了鱼油对大鼠心肌细胞膜上β－受体和腺苷酸环化酶（AC）活性的影响。鱼油1.4ml/kg每天灌胃两周对大鼠心肌细胞膜上腺苷酸环化酶（AC）的基础活性无显著影响，但可显著地抑制导丙肾上腺素（ISO）激活的AC活性，放射配体饱和实验结果显示，同正常对照相比，鱼油的摄入对Bmax和Kd无显著影响，但同羊油组相比，可显著地降低β－受体与其配体的亲和力，同正常对照相比，羊油的摄入一方面可显著地升高β－受体与其配体的亲和力，另一方面又可显著地降低β－受体的数目。结果提示，鱼油可能主要影响AC的激活而不是主要影响β－受体本身的功能。     

鱼油对大鼠心肌细胞膜上β－受体和腺苷酸环化酶活性的影响

本文探讨了鱼油对大鼠心肌细胞膜上（－受体和腺苷酸环化酶（ＡＣ）活性的影响。鱼油１．４ｍｌ／ｋｇ每天灌胃两周对大鼠心肌细胞膜上腺苷酸环化酶（ＡＣ）的基础活性无显著影响，但可显著地抑制异丙肾上腺素（ＩＳＯ）激活的ＡＣ活性。放射配体饱和实验结果显示，同正常对照相比，鱼油的摄入对Ｂｍａｘ和Ｋｄ无显著影响，但同羊油组相比，可显著地降低β－受体与其配体的亲和力，同正常对照相比，羊油的摄入一方面可显著地升高β－受体与其配体的亲和力，另一方面又可显著地降低β－受体的数目。结果提示，鱼油可能主要影响ＡＣ的激活而不是主要影响β－受体本身的功能     

Assay of Adenylate Cyclase in Rat Brain Homogenates and Lysed Turkey Erythrocytes: Two Different Methods give Different Results with Brain but not with Erythrocytes

Abstract: Experiments showed that the cyclic AMP (cAMP) fraction isolated by alumina or Dowex 50/ alumina chromatography from brain adenylate cyclase reaction mixtures contained “P radioactivity 10–12 times in excess of that which could be accounted for by determination of cAMP using binding assays. No such discrepancy was found when lysed turkey erythrocytes were assayed. This indicated that special precautions must be taken for the purification of ³²PcAMP from brain adenylate cyclase assays due to the formation of ³²P-labelled contaminants.     

Effects of Hepatic Inducers on Testicular Epoxide-Metabolizing Enzymes in the Rat and Mouse

Effects of Hepatic Inducers on Testicular Epoxide-MetabolizingEnzymes in the Rat and Mouse. DIBIASIO, K. W., SILVA, M. H.,HAMMOCK B. D., AND SHULL, L. R. (1989). Fundam. Appl. Toxicol.12, 449–459. Testicular toxicants have become of increasingimportance, necessitating a better understanding of the possiblerole of testicular xenobiotic metabolism. The responsivenessof testicular microsomal epoxide hydrolase (mEH), cytosolicepoxide hydrolase (cEH), and cytosolic glutathione S-transferase(cGST to hepatic inducers was studied in sexually mature maleF344 rats and CD-1 mice. The hepatic inducers employed werephenobarbital (PB), ß-naphthoflavone (BNF), and butylatedhydcoxyanisole (BHA) which are known to induce cytochrome P-450,cytochrome P-448, and cGST, respectively. Hepatic mEH, cEH,and cGST activities were assessed as positive controls. Measurableactivities of all enzymes studied were present in the testesof both rats and mice. PB, BNF, and BHA produced the expectedeffects on mEH, cEH, and cGST in rat and mouse livers, whereasthe testes were generally nonresponsive to the inducers. Inductionof testicular cGST by PB occurred in mice but not rats and wasthe only testicular effect produced by the hepatic inducersin this study.     

乙酰半胱氨酸对四氯化碳诱导的原代培养大鼠肝细胞损伤的保护作用

目的观察乙酰半胱氨酸（NAC）对四氯化碳（CCl4）诱导的原代培养大鼠肝细胞损伤的作用。方法在24孔细胞培养板上,用CCl4诱导原代培养肝细胞损伤,分别加入不同浓度的NAC,培养20 h后,测定上清液谷草转移酶（AST）活性,并MTT法检测细胞活力。结果 NAC在100μmol.L-1内,对正常培养的大鼠肝细胞没有影响;在4～100μmol.L-1内,NAC能剂量依赖性地抑制CCl4诱导的肝细胞活性的降低,EC50约为20μmol.L-1;当浓度为100μmol.L-1时,可以逆转CCl4诱导的肝损伤,使肝细胞释放AST降到接近正常水平,并明显改善肝细胞形态学变化。结论 NAC对CCl4诱导的肝损伤具有保护作用。     

阿米洛利对大鼠肝星状细胞增殖的影响

目的：探讨阿米洛利对大鼠肝星状细胞(HSC)增殖的影响。方法：将HSC T6细胞与不同浓度的阿米洛利共同培养24 h。MTT法观察阿米洛利对HSC T6增殖的效应，以乳酸脱氢酶(LDH)法观察阿米洛利对HSC T6的毒性作用。结果：阿米洛利浓度＞1.875 μmol·L 1时对HSC增殖有抑制作用(P＜0.01)，1.875～60 μmol·L 1未发现阿米洛利对HSC有毒性作用(P＞0.05)。结论：阿米洛利可抑制HSC的增殖，其作用不是非特异性细胞毒作用所致。     

Bioengineering of Bordetella pertussis Adenylate Cyclase Toxin for Vaccine Development and Other Biotechnological Purposes

The adenylate cyclase toxin, CyaA, is one of the key virulent factors produced by Bordetella pertussis, the causative agent of whooping cough. This toxin primarily targets innate immunity to facilitate bacterial colonization of the respiratory tract. CyaA exhibits several remarkable characteristics that have been exploited for various applications in vaccinology and other biotechnological purposes. CyaA has been engineered as a potent vaccine vehicle to deliver antigens into antigen-presenting cells, while the adenylate cyclase catalytic domain has been used to design a robust genetic assay for monitoring protein–protein interactions in bacteria. These two biotechnological applications are briefly summarized in this chapter.     

Effects of Methapyrilene on Rat Hepatic Xenobiotic Metabolizing Enzymes and Liver Morphology

Effects of Methapyrilene on Rat Hepatic Xenobiotic MetabolizingEnzymes and Liver Morphology. GRAICHEN, M. E., NEPTUN, D. A.,DENT, J. G., POPP, J. A., AND LEONARD, T. B. (1985). Fundam.Appl. Toxicol. 5, 165–174. Short-term treatment of ratswith hepatocarcinogens elicits a consistent pattern of phenotypicchanges in hepatic drug metabolizing enzymes, the most strikingof which is a marked increase in microsomal epoxide hydrolase(EH) activity. The antihistaminic drug methapyrilene inducesa high incidence of hepatocellular carcinoma in F-344 rats.The studies reported here were designed to assess the effectsof methapyrilene on hepatic EH activity, cytochrome P-450-dependentmixed-function oxidase activities, liver morphology, and liver-derivedserum enzymes. Male F-344 rats were treated with three dailyoral doses of methapyrilene-HG, up to 300 mg/kg/day, and weresacrificed 48 hr after the last dose. Hepatic microsomal EHand cytosolic DT-diaphorase activities were increased in a dose-relatedfashion, to 420 and 230% of control, respectively. CytochromeP-450 content and benzphetamine-N-demethylase and ethoxycoumarin-O-deethylaseactivities were concomitantly decreased to 35–50% of control.Serum -glutamyl transpeptidase and alanine aminotransferaseactivities were elevated 22- to 27-fold, and serum bile acidsto 36-fold by treatment with methapyrilene. Periportal lesions,characterized by inflammation, nuclear and nucleolar enlargement,bile duct hyperplasia, and hepatocellular necrosis, were observedfollowing methapyrilene administration. The severity of theperiportal lesion correlated with elevations in the serum chemistryparameters. The increases noted in microsomal EH activity supportsthe suggestion that this enzyme may be a useful biochemicalmarker for exposure to hepatocarcinogens.     

Effect of Opioid Agonists Selective for Three Subclasses of Opioid Receptors and One σ Receptor Agonist on Dopamine Stimulated Adenylate Cyclase in Rat Caudate Nucleus

Abstract: The adenylate cyclase in rat caudate nucleus homogenate could be stimulated by dopamine and less potently by the dopamine D₁ receptor specific agonist SKF38393. Agonists selective for μ[D-Ala², MePhe⁴Gly(o1)⁵]enkephalin (DAGO) and δ opioid receptors [D-Pen², D-Pen⁵]enkephalin (dPen-dPen), inhibited the dopamine but not the dopamine D₁ stimulated adenylate cyclase. The opioid agonist, U69593, had no effect, probably due to low kappa receptor contents in rat caudate nucleus. 10^?4 M of the σ receptor specific agonist, 1,3-di-o-tolylguanidine (DTG), potentiated the dopamine as well as the dopamine D₁ stimulated adenylate cyclase while lower concentrations of DTG had no effect.     

门冬氨酸鸟氨酸联用治疗肝性脑病

目的分析门冬氨酸和鸟氨酸联合治疗肝性脑病的临床疗效。方法收集了因乙肝肝硬化、丙肝肝硬化或重症乙型肝炎出现的肝性脑病患者50例,随机分为门冬氨酸、鸟氨酸治疗组（n=30）和乙酰谷酰胺治疗组（n=20）,治疗10d后观察疗效。结果门冬氨酸和鸟氨酸治疗组显效14例（46．7％）,有效14例（46．7％）,无效2例（6．6％）,无死亡,总有效率为93．3％;而乙酰谷酰胺组显效6例（30．0％）,有效7例（35．0％）,无效5例（25．0％）,死亡2例（10．0％）,总有效率为65．0％,两组总有效率比较差异有显著性（P〈0．05）。结论门冬氨酸和鸟氨酸是治疗肝性脑病的有效药物,可迅速控制患者的临床症状,降低死亡。