Gene/Protein Disease Symptom Drug Enzyme Compound
Pivot Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound   Target Concepts: Gene/Protein Disease Symptom Drug Enzyme Compound

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Query: EC:4.6.1.1 (adenylate cyclase)
19,190 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

On the basis of the information presented in this review, it is difficult to reach any firm decision regarding the role of cyclic AMP (or cyclic GMP) in synaptic transmission in the brain. While it is clear that cyclic nucleotide levels can be altered by the exposure of neural tissues to various neurotransmitters, it would be premature to claim that these nucleotides are, or are not, essential to the transmission process in the pre-or post-synaptic components of the synapse. In future experiments with cyclic AMP it will be necessary to consider more critically whether the extracellularly applied nucleotide merely provides a source of adenosine and is thus activating an extracellularly located adenosine receptor, or whether it is actually reaching the hypothetical sites at which it might act as a second messenger. The application of cyclic AMP by intrcellular injection techniques should minimize this particular problem, although possibly at the expense of new diffulties. Prio blockade of the adenosine receptor with agents such as theophylline or adenine xylofuranoside may also assist in the categorization of responses to extracellularly applied cyclic AMP as being a result either of activation of the adenosine receptor or of some other mechanism. Utimately, the developement of highly specific inhibitor for adenylate cyclase should provide a firm basis from which to draw conclusions about the role of cyclic AMP in synaptic transmission. Similar considerations apply to the action of cyclic GMP and the role of its synthesizing enzyme, guanylate cyclase. The use of phosphodiesterase inhibitors in studies on cyclic nucleotides must also be approached with caution. The diverse actions of many of these compounds, which include calcium mobilization and block of adenosine uptake, could account for many of the results that have been reported in the literature.
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PMID:The role of cyclic nucleotides in the CNS. 1 46

1. Dibutyryl cyclic AMP (Db cAMP, 75-500 microgram/kg), injected into the lateral ventricle of the brain of the cat increased blood pressure, heart rate and splanchnic discharge rate. 2. ATP, but not AMP, induced similar changes; GMP in small doses increased blood pressure. 3. A number of drugs are known to activate adenylate cyclase-induced hypertension, tachycardia and increase splanchnic discharge rate. This was shown for TRH, tetracosactide and a new beta2-adrenoceptor stimulant, NAB 365. 4. Injection into the lateral ventricle of theophylline or Ro 7/2956, both inhibitors of phosphodiesterase, similarly increased blood pressure. 5. Histamine administered by the same route induced similar reactions; it is not known if this action was exerted by activation of H1- or H2-receptors. 6. Somatostatin, known to reduce cAMP levels, induced a small but significant decrease in blood pressure. Melanocyte stimulating hormone release inhibiting factor (MIF) and TSH were ineffective. 7. These results provide evidence for the possibility of a role for cAMP in the central regulation of blood pressure at suprabulbar levels.
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PMID:Cyclic 3'5'-adenosine monophosphate and central circulatory control in cats and dogs. 2 Feb 56

Based on the current experimental evidence, a model is proposed for mutual interactions of histamine, prostaglandins, and cyclic AMP in regulation of gastric secretion and pathogenesis of peptic ulcer. Histamine acting on H2-receptor-associated adenylate cyclase stimulates cyclic AMP formation and consequently secretion of hydrochloric acid in oxyntic cells. Prostaglandins (mainly E type) in another cell population stimulate cyclic AMP formation which may lead to formation of glycosaminoglycans and glycoproteins. Glycosaminoglycans and glycoproteins may have antisecretory and cytoprotective properties. In addition to this effect, prostaglandin endoperoxides may inhibit histamine-stimulated cyclic AMP formation in oxyntic cells.
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PMID:Interrelationships between histamine, prostaglandins, and cyclic AMP in gastric secretion: a hypothesis. 2 Mar 85

The norepinephrine-sensitive adenylate cyclase system in the rat brain was examined. Adrenergic blocking agents and the relative activity of structurally related catecholamines were employed to determine whether norepinephrine-stimulated accumulation of [3H]c-AMP in the hypothalamus occurred via alpha or beta adrenergic receptors. The results indicate that norepinephrine probably acts through a mixture of alpha and beta receptors in that both alpha and beta adrenergic blockers inhibited norepinephrine-induced accumulation of [3H]c-AMP. Morphine and levorphanol had no significant effect on adenylate cyclase or phosphodiesterase activities in hypothalamic slices or homogenates of several brain regions.
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PMID:Norepinephrine-sensitive adenylate cyclase in rat hypothalamus: effects of adrenergic blockers and narcotics. 2 29

The effects of dopaminergic agonists and antagonists have been studied in dispersed bovine parathyroid cells. Dopaminergic agonists caused a transient 20- to 40-fold increase in cellular cyclic AMP and a 2- to 3-fold increase in parathyroid hormone release. Dose-response relationships were similar for cyclic AMP accumulation and hormone release, whether studied by increasing agonist concentration or by increasing concentration of antagonist with constant agonist. The effects on the dopamine receptor could be differentiated from those of the previously characterized beta-adrenergic receptor by specific inhibitors. These results appear to represent proof with a homogeneous cell population that dopaminergic receptors linked to adenylate cyclase can regulate a secretory process mediated by cyclic AMP. This system should be useful in further studies on dopamine receptors and should provide a valid tool for determining interactions of radiolabeled ligands with such receptors.
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PMID:Dopaminergic stimulation of cyclic AMP accumulation and parathyroid hormone release from dispersed bovine parathyroid cells. 2 76

The dopamine (DA)-sensitive adenylate cyclase in the substantia nigra was assayed in rats which had been subjected to 3 different kinds of brain lesion: (1) unilateral 6-hydroxydopamine (6-OHDA) lesions of the medial forebrain bundle; (2) unilateral lesions of the descending strio-nigral and pallido-nigral projections; (3) total lesions of the serotoninergic raphe-nigral pathway. Lesions of the medial forebrain bundle causing 97% depletion of striatal DA, 72% depletion of nigral tyrosine hydroxylase, and no change in nigral glutamate decarboxylase (GAD), resulted in no change in basal or DA-stimulated cyclic AMP production ipsilateral to the injection. Lesions of the globus pallidus, causing 70% and 79% reductions in GAD and substance P respectively in the ipsilateral nigra, produced a reduction in basal cyclic AMP production and abolished the normal increase in cyclic AMP produced by DA on the side of the lesion. Lesions to the dorsal and median raphe nuclei did not affect the normal DA-sensitive adenylate cyclase response in the nigra. The results suggest that one of the neurotransmitter functions of DA in this brain region may be to modulate the release of psi-aminobutyric acid (GABA) or substance P from synaptic terminals afferent to the nigra.
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PMID:Evidence concerning the anatomical location of the dopamine stimulated adenylate cyclase in the substantia nigra. 2 89

The aim of the present work was to explain the mechanism of the stimulating effect of adrenaline (A) on acetylcholine (ACh) synthesis. This action is exerted most probably through the beta- adrenergic receptors, since propranolol and oxprenolol inhibit the stimulating effect of adrenaline on acetylcholine synthesis in the rat cerebral cortex in vitro. Dihydroergotamine does not show such effect. Practolol and phentolamine decrease the spontaneous synthesis of ACh in concentration several times lower than that inhibiting the ACh synthesis stimulated by adrenaline. It is suggested that adrenaline-induced stimulation of ACh synthesis in the rat cerebral cortex is not due to cyclic AMP, because noradrenaline (NA) does not increase ACh synthesis either in vivo or in vitro, although it activates the adenyl cyclase. NA on the other hand activates ACh synthesis in the calcium-free medium, which inhibits activating effect of NA on adenyl cyclase. Moreover it was found that cyclic AMP depresses ACh synthesis in the rat cerebral cortex in vitro.
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PMID:The effect of adrenaline on acetylcholine synthesis after blockade of alpha- and beta-adrenergic receptors in vitro. 2 84

In dissociated single cells from the sponge Geodia cydonium, DNA synthesis is initiated after incubation with a homologous, soluble aggregation factor. During the DNA-initiation phase the cyclic AMP- and cyclic GMP levels vary drastically; the cyclic AMP content drops from 2.2 pmol/10(6) cells to 0.3 pmol/10(6) cells while the cyclic GMP content increases from 0.6 pmol to 3.7 pmol/10(6) cells. The activity of neither the adenylate cyclase nor of the guanylate cyclase isolated from cells which have been incubated for different periods of time with the aggregation factor, is changed. The soluble as well as the particulate enzyme activities were checked in vitro. The cyclic nucleotide receptors have been isolated from the sponge cells and characterized with respect to their molecular weight, dissociation constant for cyclic AMP or cyclic GMP and intracellular concentration. None of these parameters are altered during aggregation factor-mediated DNA initiation. From these data it is concluded that the regulation of cyclic nucleotide levels is a consequence of a changed activity of nucleotide cyclases or of phosphodiesterases, but this is presumably not caused by a changed rate of synthesis of nucleotide cyclases or of cyclic nucleotide receptors.
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PMID:Species-specific aggregation factor in sponges. VII. Its effect on cyclic amp and cyclic gmp metabolism in cells of Geodia cydonium. 2 1

Malignant myeloid leukemic cells and normal macrophages and granulocytes have functional beta-adrenergic receptors, which have been quantitated by radioreceptor binding with the beta-adrenergic antagonist [(3)H]dihydroalprenolol and by induction of cyclic AMP by adrenergic hormones. Both the normal and leukemic cells have beta(2)-adrenergic receptors, and the [(3)H]dihydroalprenolol binding was saturable, reversible, and stereospecific. The leukemic cells consisted of clones that could be induced to differentiate (MGI(+)D(+)) and clones that could not be induced to differentiate to mature macrophages and granulocytes by the protein inducer MGI. The different types of leukemic clones all had 1100-2300 receptor sites per cell, whereas normal macrophages had 7000 receptors per cell. The differentiation of MGI(+)D(+) leukemic cells was associated with an increase in receptors to a number similar to that found with normal macrophages. MGI(+)D(+) leukemic cells and normal macrophages were able to densensitize to the beta-adrenergic agonist (-)isoproterenol, shown by termination of cyclic AMP induction within 10-15 min and the lack of a second induction. The leukemic cells that could not be induced to differentiate lacked this capacity for desensitization, possibly due to an alteration in the uncoupling system between the receptor and adenylate cyclase. The lack of desensitization in these leukemic cells was associated with a higher sensitivity to the receptor-mediated cytotoxic effects of adrenergic hormones. It is suggested that cells, like some leukemic cells, that are unable to desensitize to adrenergic and possibly other hormones may be appropriate targets for differential destruction by hormones under conditions that do not affect normally desensitizing cells.
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PMID:Differential desensitization of functional adrenergic receptors in normal and malignant myeloid cells: relationship to receptor-mediated hormone cytotoxicity. 2 40

In selected beta1- (heart, lipolysis) and beta2-adrenoceptor (trachea) systems, the interaction of racemic-trimetoquinol (TMQ) and the erythro- and threo-diastereomers of 1-(3',4',5'-trimethoxy-alpha-hydroxybenzyl)-6,7-dihydroxy-1,2,3,4-tetrahydroisoquinoline (alpha-hydroxy TMQ) was investigated. Each tetrahydroisoquinoline possessed agonist activity in these beta-adrenoceptor systems. The rank order of potency observed for these compounds was racemic-TMQ greater than erythro-alpha-hydroxy TMQ greater than threo-alpha-hydroxy TMQ. Using isolated fat adipocytes, a favorable correlation was observed between the elevation in c-AMP and pharmacological response for the TMQ stereoisomers and diastereomers of alpha-hydroxy TMQ. The rise in intracellular c-AMP produced by (-)- and (+)-TMQ in fat cells was blocked by the presence of propranolol, and not in the presence of phentolamine. Since considerably higher concentrations (greater 10(-4) M) of these compounds were required to produce a significant inhibition of c-AMP phosphodiesterase activity in adipose tissue, it is proposed that the lipolytic response is a result of stereoselective interaction of these tetrahydroisoquinolines at the level of membrane-bound adenylate cyclase.
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PMID:Stereoselective interaction of tetrahydroisoquinolines in beta-adrenoceptor systems. 2 78


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