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)

1. The activities of the enzymes involved in the metabolism of cyclic nucleotides were studied in sarcolemma prepared front guinea-pig heart ventricle; the enzyme activities reported here were linear under the assay conditions. 2. Adenylate cyclase was maximally activated by 3mM-NaF; NaF increased the Km for ATP (from 0.042 to 0.19 mM) but decreased the Ka for Mg2+ (from 2.33 to 0.9 mM). In the presence of saturating Mg2+ (15 mM), Mn2+ enhanced adenylate cyclase, whereas Co2+ was inhibitory. beta-Adrenergic amines (10-50 muM) stimulated adenylate cyclase (38+/-2%). When added to the assay mixture, guanyl nucleotides (GTP and its analogue, guanylyl imidophosphate) stimulated basal enzyme activity and enhanced the stimulation by isoproterenol. By contrast, preincubation of sarcolemma with guanylyl imidodiphosphate stimulated the formation of an 'activated' form of the enzyme, which did not reveal increased hormonal sensitivity. 3. The guanylate cyclase present in the membranes as well as in the Triton X-100-solubilized extract of membranes exhibited a Ka for Mn 2+ of 0.3 mM; Mn2+ in excess of GTP was required for maximal activity. Solubilized guanylate cyclase was activated by Mg2+ only in the presence of low Mn2+ concentrations; Ca2+ was inhibitory both in the absence and presence of low Mn2+. Acetylcholine as well as carbamolycholine stimulated membrane-bound guanylate cyclase. 4. Cylic nucleotide phosphodiesterase activities of sarcolemma exhibited both high-and low-Km forms with cyclic AMP and with cyclic GMP as substrate. Ca2+ ions increased the Vmax. of the cyclic GMP-dependent enzyme.
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PMID:Adenylate cyclase, guanylate cyclase and cyclic nucleotide phosphodiesterases of guinea-pig cardiac sarcolemma. 1 Aug 95

The sarcolemma fraction with a considerable adenylate cyclase activity sensitive to adrenalin is isolated from the rabbit skeletal muscles. Some its properties are established: pH-optimum of the activity, stability in storage and resistance to the effect of different pH and temperature. Acetylcholine and ruthenium red do not affect the adenylate cyclase activity of the sarcolemma. EGTA activates and Ca2+ inhibits it having no effect on sensitivity to adrenalin.
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PMID:[Properties of adenylate cyclase of rabbit skeletal muscle sarcolemma]. 10 69

Smooth muscle cells of the newborn guinea-pig vas deferens dispersed into single cells and grown in culture maintain their differentiation for approximately 5 days before undergoing dedifferentiation and mitosis. The presence of sympathetic nerve fibres in contact with the isolated cells delays this process by 3-7 days (Chamley et al., 1974). A similar delay in dedifferentiation of vas deferens smooth muscle cells in tissue culture in the presence of sympathetic ganglion extract is described in the present report, demonstrating that the trophic effect is elicited by a chemical substance. This effect is mimicked by the presence of either a confluent layer of RKA epithelial cells, dibutyryl cyclic AMP or theophylline. A similar, but considerably weaker, effect is also obtained with spinal cord and liver extracts and noradrenaline. Acetylcholine does not show an effect. It is suggested that a trophic substance (probably not noradrenaline) from sympathetic neurons activates the adenyl cyclase system of smooth muscle cells to increase the intracellular level of cyclic AMP which in turn promotes and maintains the differentiation of the cultured smooth muscle cells.
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PMID:Trophic influences of sympathetic nerves and cyclic AMP on differentiation and proliferation of isolated smooth muscle cells in culture. 16 97

The presence and production of cyclic 3', 5'-adenosine monophosphate (cAMP) were investigated in the hypothalamus and neural lobe of the rat. Theophylline (concentrations from 10(-3) to 8 X 10(-3) M) increased the in vitro content of cAMP in the isolated neural lobe and in hypothalamic tissue samples containing supraoptic (SO) or paraventricular (PV) nuclei. Acetylcholine (ACH; 10(-2) and 10(-4) M) or carbachol (10(-4) M) did not increase cAMP content in the isolated neural lobe. Small increases were apparent (p less than 0.05, t-test for paired samples) in the hypothalamus. The amounts of cAMP were significantly higher in isolated neural lobes but not in hypothalami of NaCl-treated or lactating as compared to control rats. Presence of cAMP in the neural lobe and activation of adenylate cyclase under stimulated hormone release conditions indicate a possible involvement of cAMP in the process of neurohypophysial hormone secretion.
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PMID:Cyclic 3'5'-adenosine monophosphate in the hypothalamo-neurohypophysial system of normal, NaCl-treated and lactating rats. 19 64

Catecholamine release and cAMP accumulation were studied in bovine adrenal medulla slices in vitro. Acetylcholine (10(-4) M) and salbutamol (10(-6) M) caused increased release of catecholamines and accumulation of cAMP. Incubation in Ca2+ -free medium abolished the release of catecholamines and the increase of cAMP caused by acetylcholine but not that caused by salbutamol. In a membrane fraction of adrenal medulla acetylcholine (10(-4) M) had no effect on adenylate cyclase activity but salbutamol (10(-6) M) caused substantial activation of adenylate cyclase. It is suggested that acetylcholine has no direct effect on adenylate cyclase or cAMP in adrenal medulla and the accumulation of cAMP observed in slices incubated with acetylcholine is due to the effect of catecholamines, released by acetylcholine, on the medullary cells.
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PMID:Acetylcholine and cAMP in adrenal medulla:indirect effect. 19 28

Catecholamine (CA) secretion from the adrenal medulla was induced in vitro by acetylcholine (10(-4)M) (ACh), by incubation in potassium-free medium, by addition of ouabain (10(-3)M), by theophylline (10(-2)M) or by salbutamol (10(-6) and 6 x 10(-6) M). Theophylline and salbutamol, but not ACh, released CA in a calcium-free medium supplemented with 2mM EGTA. PGE2 significantly inhibited both CA secretion evoked by ACh and that evoked by salbutamol, i.e. both secretion dependent on, and independent of, extracellular calcium, PGE2 counteracted the increase of cAMP levels caused by ACh or salbutamol in adrenal medullary slices. PGE2 also diminished the salbutamol-induced activation of adenylate cyclase in an adrenal medullary membrane preparation, PGE2 reduced the rate of 45Ca efflux from slices of adrenal medulla preloaded with 45CaCl2. It is suggested that PGE2 inhibits CA secretion through the following sequence: inhibition of adenylate cyclase, a fall of cellular cAMP resulting in reduced release of calcium from intracellular binding sites and reduced free cytoplasmic calcium.
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PMID:Mechanism of PGE inhibition of catecholamine release from adrenal medulla. 22 95

In open-chest dogs anesthized with sodium pentobarbital, acetylcholine (ACh, 5 times 10'-5M) infused into the left circumflex coronary artery caused an increase in coronary flow and a decrease in myocardial O'2 extraction ratio (P less than .01) anduptake (P less than .05). Heart rate and mean arterial pressure were not altered,although left ventricular dP/dt declined from 2,037 plus or minus 205 to 1,873 plus or minus 194 mmHg/s (P less than .02). Intracoronary administration of norepinephrine (NE, 2.4 times 10'-6M) caused an increase in myocardial O'2 uptake (P less than .02); simultaneous infusion of both NE and ACh caused a decline in O'2 extraction ratio (P less than .01) and uptake (P less than 0.5). Myocardial adenylatecyclase activity in response to ACh was not altered significantly from a control levelof 188 plus or minus 22 pmol of '14C-labeled cyclic AMP/mg protein per 10 min. Norepinephrine alone elevated adenylate cyclase activity to 401 plus or minus 45 pmol ['14C]cyclic AMP/mg protein per 10 min (P less than .01). However, with simultaneous infusion of both NE and ACh, adenylate cyclase returned to control levels. Although ACh alone did not alter myocardial hormone-sensitive lipaseactivity, NE elevated lipolytic activity from 8.1 plus or minus .7 to 13.2 plus or minus 1.8 mueq free fatty acid (FTA)/g per 30 min (P less than .05). The administration of both ACh and NE returned lipase activity to nearly control levels. Myocardial uptake of FFA increased significantly during ACh infusion alone (P less than 0.5) and during NE infusion alone (P less than 905). However, when NE and AChwere administered together, a decline in FFA uptake was observed (P less than .02). These data indicate that the effects of ACh on cardiac metabolism are minimal, withthe decline in myocardial O'2 uptake of ACh primarily reflecting the decrease in contractility. On the other hand, antagonism of ACh on NE-stimulated myocardial lipid metabolism appears to involve activity of the adenylate cyclase system.
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PMID:Acetylcholine and norepinephrine interactions on cardiac lipids and hemodynamics. 115 99

The release of 14C-ACh from rat nucleus accumbens slices, induced by 15 mM [K+], was inhibited by the mu- and delta-opioid agonists DAMGO and DPDPE, respectively, whereas only the kappa agonist U50,488 reduced the release of 3H-DA. The opioid receptors involved appear to be localized on nerve terminals, since blockade of action potential propagation by 1 microM TTX did not diminish the inhibitory effects of DAMGO, DPDPE or U50,488. Enhancement of the potassium concentration in the superfusion medium to 56 mM with simultaneous reduction of the Ca2+ concentration from 1.2 mM to 0.12 mM induced a release similar to that caused by 15 mM K+ and 1.2 mM Ca+. Under this conditions, the inhibitory effects of both DAMGO and DPDPE on stimulated 14C-ACh release were reduced, whereas the inhibition of evoked 3H-DA release caused by U50,488 was not affected. Activation of mu- as well as delta-opioid receptors by DAMGO and DPDPE, respectively, inhibited forskolin-stimulated adenylate cyclase activity. However, increasing the intracellular cAMP levels with 0.3 mM 8-bromo-cAMP affected neither the depolarization-induced release of 14C-ACh or 3H-DA from accumbens slices nor the inhibitory effects of opioid receptor activation thereon. The results indicate that the mechanism by which functional mu and delta receptors presynaptically inhibit the depolarization-induced 14C-ACh release from nucleus accumbens slices is likely to involve an increase of potassium channel conductance. In contrast, activation of kappa-opioid receptors, which inhibits depolarization-evoked 3H-DA release, apparently does not result in a hyperpolarization of (dopaminergic) nerve terminals. In none of these inhibitory effects presynaptic adenylate cyclase appears to be involved.
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PMID:Opioid receptor-mediated inhibition of 3H-dopamine and 14C-acetylcholine release from rat nucleus accumbens slices. A study on the possible involvement of K+ channels and adenylate cyclase. 132 56

1. The signal transduction pathway for vasorelaxation induced by human alpha-calcitonin gene-related peptide (human alpha-CGRP) was studied in rat thoracic aortic rings preconstricted with noradrenaline (10(-7) M). 2. Vasorelaxation by human alpha-CGRP was inhibited by haemoglobin (10(-6) M) and methylene blue (10(-5) M) but was unaffected by ibuprofen (10(-5) M). 3. Acetylcholine caused a 16 fold increase in levels of guanosine 3':5'-cyclic monophosphate (cyclic GMP) with levels of adenosine 3':5'-cyclic monophosphate (cyclic AMP) being unaltered. Human alpha-CGRP caused a 12 fold increase in levels of cyclic GMP but, in contrast to acetylcholine, evoked a 2.5 fold rise in levels of cyclic AMP. The rises in cyclic nucleotides evoked by human alpha-CGRP and acetylcholine were dependent on the presence of an intact endothelium. 4. NG-nitro-L-arginine (L-NOARG: 10(-5) M), which inhibits nitric oxide synthetase, inhibited the relaxant response to human alpha-CGRP and cyclic GMP accumulation without affecting the cyclic AMP accumulation. 5. The data presented in this paper suggests that human alpha-CGRP relaxes the rat thoracic aorta by releasing nitric oxide and stimulating guanylate cyclase. The stimulation of adenylate cyclase by human alpha-CGRP probably precedes the activation of nitric oxide synthase but could be unrelated to the relaxant response.
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PMID:Human alpha-calcitonin gene-related peptide stimulates adenylate cyclase and guanylate cyclase and relaxes rat thoracic aorta by releasing nitric oxide. 136 70

We examined the effects of calcitonin gene-related peptide (CGRP) on the membrane currents of single atrial and ventricular cells of guinea pig heart. The tight-seal whole-cell voltage-clamp technique was used. In atrial cells, like isoproterenol, CGRP increased the L-type Ca channel current (ICa.L) in a concentration-dependent manner. Human CGRP-(8-37), a putative CGRP receptor antagonist, completely abolished the CGRP-induced increase of ICa.L. Although the effects of CGRP were similar to those of isoproterenol, propranolol, a beta-adrenergic receptor antagonist, did not affect the CGRP-induced increase of ICa.L. After ICa.L had been maximally activated by isoproterenol (2 microM) or intracellular cyclic adenosine 5'-monophosphate (100 microM), CGRP failed to increase ICa.L. Acetylcholine antagonized the effects of CGRP on ICa.L. Unlike the effects on atrial cells, CGRP had no significant effects on the membrane currents of ventricular myocytes. These results indicate that CGRP increases ICa.L via adenylate cyclase activation by binding to specific membrane receptors in cardiac atrial myocytes. Furthermore, CGRP receptors are expressed in atrial cells but probably not in ventricular cells.
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PMID:Effects of calcitonin gene-related peptide on membrane currents in mammalian cardiac myocytes. 166 40


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