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Showing papers on "Cyclase published in 1972"


Journal ArticleDOI
TL;DR: Hormonal stimuli causing marked increases in cAMP in vivo or in vitro did not affect the level of cGMP, indicating that the concentration of each of these nucleotides is controlled independently.

531 citations


Journal ArticleDOI
TL;DR: Data indicate that marked inhibition by nucleosides of the increase in total cyclic AMP accumulation seen 5 min after the addition of theophylline, norepinephrine, or nore Pinephrine plus theophyLLine is not necessarily associated with any decrease in lipolysis.

308 citations


Journal ArticleDOI
TL;DR: A catecholamine-sensitive adenylate cyclase system is present in homogenates of both calf and rat retinas, and it is proposed that dopamine is the major activator of a retinalAdenylates cyclase, and that this activation is related to its role as a neurotransmitter.
Abstract: A catecholamine-sensitive adenylate cyclase system is present in homogenates of both calf and rat retinas. Dopamine is a more potent activator of the bovine enzyme than is norepinephrine or epinephrine. Cyclic AMP concentrations in intact bovine retina are increased by dopamine, as well as by other catecholamines, and by depolarizing agents. Studies with adrenergic blocking agents suggest that the stimulation of retinal adenylate cyclase by catecholamines cannot be clearly defined in terms of the characteristics of alpha or beta adrenergic receptors. Bovine retina also contains a protein kinase that is stimulated 20-fold by cyclic AMP. It is proposed that dopamine is the major activator of a retinal adenylate cyclase, and that this activation is related to its role as a neurotransmitter.

282 citations


Journal ArticleDOI
25 Feb 1972-Science
TL;DR: Direct effects of insulin on an enzymatic system in broken-cell -preparations suggest a fundamental role of adenylate cyclase activity and of cyclic adenosine monophosphate in the mechanism of action of insulin.
Abstract: Insulin depresses both the activity of adenylate cyclase stimulated by glucagon, epinephrine, and sodium fluoride in liver cell membranes and the activity of adenylate cyclase stimulated by epinephrine and adrenocorticotropin in particulate preparations from homogenates of isolated fat cells. Significant inhibition is detected with very low concentrations (10 -11 molar) of insulin but not with unphysiologically high (10 -9 molar) concentrations of the hormone. These direct effects of insulin on an enzymatic system in broken-cell -preparations suggest a fundamental role of adenylate cyclase activity and of cyclic adenosine monophosphate in the mechanism of action of insulin.

226 citations


Journal ArticleDOI
TL;DR: The data suggest at least 2 mechanisms by which gluoocorticosteroids benefit asthmatic patients: Increased activity of adenyl cyclase, and Restoration ofAdenyl Cyclase responsiveness to catecholamines.
Abstract: To evaluate the theory of beta-adrenergic blockade in asthma, we measured the effects of hydrocortisone and isoproterenol on adenyl cyclase in peripheral blood leukocytes from asthmatic and nonasthmatic children and nonasthmatio adults. An intact cell method was used, allowing cells to incorporate 3 H-adenine and convert it to 3 H-adenosine triphosphate (ATP) during a 2 hour incubation. Experimental compounds were then added for a pulse exposure of 5 minutes. AdenyZ cyclase catalyzes the transformation of 3 H-ATP to 3 H-cyclic adenosine monophosphate (AMP), which was measured after chromatographic separation. To rule out effects on rate of cyclic AMP destruction, aminophylline was routinely added at 25 mM., a concentration which completely inhibited cyclic AMP phosphodiesterase. Hydrocortisone at 10 −6 M stimulated adenyl cyclase in leukocytes from all subjects by 24 to 85 per cent. Isoproterenol at 10 −6 M stimulated adenyl cyclase by 16 to 19 per cent in control subjects, but not in cells from asthmatic subjects, a finding which supports the beta-adrenergic blockade hypothesis. Children receiving glucocorticosteroid therapy showed a restoration of leukocyte adenyl cyclase responsiveness to Isoproterenol. No synergistic effects between the steroid and catecholamine were observed in vitro. The data suggest at least 2 mechanisms by which gluoocorticosteroids benefit asthmatic patients: (1) Increased activity of adenyl cyclase, and (2) Restoration of adenyl cyclase responsiveness to catecholamines.

182 citations


Journal ArticleDOI
TL;DR: Results were taken as evidence for the existence of regulatory sites binding either GTP or ATP; the occupancy of these sites enhances the velocity of the adenylate cyclase reaction to a greater extent in the presence of oxytocin than under basal conditions.

158 citations


Journal ArticleDOI
TL;DR: GTP did not appear to change the apparent affinity of the substrate to the enzyme, but markedly increased the PGE1-stimulated enzyme activity.

155 citations


Journal ArticleDOI
TL;DR: A renal plasma membrane fraction has been prepared by homogenization and differential centrifugation in an isotonic sucrose solution in 10 mm Tris, pH 7.5, and 1 mm ethylenediaminetetraacetate that showed a striking decrease in specific activity of marker enzymes for endoplasmic reticulum and brush border, but a 2.7-fold increase in thespecific activity of Na-K-ATPase.

153 citations


Journal ArticleDOI
TL;DR: The regulation of adenylate cyclase in skeletal muscle may be classified as a "V" allosteric system since metal ions, F-, and epinephrine all result in increased maximal velocity of the enzyme reaction.

151 citations


Journal ArticleDOI
TL;DR: In this paper, glucagon-sensitive, insulin-secreting tumors of the Syrian (golden) hamster were homogenized in 1 mm NaHCO3 and subjected to differential centrifugation.

143 citations


Journal ArticleDOI
TL;DR: Capillaries were isolated from epididymal fat, and a catecholamine-sensitive adenylate cyclase found in these capillaries was characterized and the cyclase was found to exhibit mixed alpha and beta characteristics.
Abstract: Capillaries were isolated from epididymal fat, and a catecholamine-sensitive adenylate cyclase found in these capillaries was characterized. The effect of various hormones on the accumulation of adenosine 3′:5′-cyclic monophosphate in capillary endothelial cells was determined and the cyclase was found to exhibit mixed alpha and beta characteristics. Cyclase was cytochemically localized in these endothelial cells with 5′-adenylyl-imidodiphosphate as a specific cyclase substrate and alloxan as a specific cyclase inhibitor. Lead imidodiphosphate was precipitated at or near the site of cyclase activity upon hydrolysis of 5′-adenylyl-imidodiphosphate by cyclase. This reaction product was observed primarily on the luminal surface of intact capillaries, in micropinocytic invaginations, in free vesicles within the cytoplasm, and in the intracellular junctions.

Journal ArticleDOI
TL;DR: The cytotoxic action of lymphocytes upon cells bearing alloantigens to which they are sensitized is inhibited by agents that elevate intracellular amounts of 3':5'-cyclic AMP, and cholinergic agents, added in the range of 1 to 100 pM, enhance cytotoxicity, an effect that is blocked by atropine.
Abstract: The cytotoxic action of lymphocytes upon cells bearing alloantigens to which they are sensitized is inhibited by agents that elevate intracellular amounts of 3′:5′-cyclic AMP: prostaglandin E1, cholera toxin, and theophylline. Cholinergic agents, added in the range of 1 to 100 pM, enhance cytotoxicity, an effect that is blocked by atropine. Because cholinergic agents elevate cyclic GMP in other in vitro systems, these findings suggest that the cytotoxic process effected by sensitized lymphocytes is a secretory phenomenon modulated by cyclic AMP and cyclic GMP.

Journal ArticleDOI
TL;DR: The results suggest that the activation and inhibition of platelet adenylatecyclase by adenosine or 2-chloroadenosine are independent processes mediated by different components of a receptor-adenylate cyclase complex.

Journal ArticleDOI
10 Mar 1972-Science
TL;DR: It is proposed that adenyl cyclase in the intact plasma membrane is located in a compartment wherein calcium concentration is low and remains unaffected by the concentration of calcium in the extracellular space, and the strength of the signal generated by the interaction of adrenocorticotropic hormone with its receptor and transmitted to the adenYL cyclase compartment is proportionately increased.
Abstract: Corticosterone production by isolated adrenal cells in response to adrenocorticotropic hormone is reduced when the cells are incubated in a medium that contains no calcium. This reduction is associated with an equal reduction of accumulation of cyclic adenosine monophosphate. Production of corticosterone and accumulation of cyclic adenosine monophosphate are increased when the calcium concentration in the medium is increased (from zero to 7.65 millimolar). This is in contrast to the situation in "subcellular membrane fragments" of adrenal tissue where high calcium in the medium (> 1.0 millimolar) inhibits cyclic adenosine monophosphate accumulation. We propose that adenyl cyclase in the intact plasma membrane is located in a compartment wherein calcium concentration is low and remains unaffected by the concentration of calcium in the extracellular space. It is proposed that, as the concentration of calcium in the incubation medium is increased from zero to 7.65 millimolar, the strength of the signal generated by the interaction of adrenocorticotropic hormone with its receptor and transmitted to the adenyl cyclase compartment is proportionately increased.

Journal ArticleDOI
TL;DR: Bovine taste buds bearing papillae exhibit high adenyl cyclase activity comparable to the activity found in the brain, while the tongue epithelium without taste buds exhibits much lower activity.

Journal ArticleDOI
TL;DR: It is concluded that glucagon reacts rapidly and reversibly with its receptor in the presence of ATP, that this interaction results in rapid and reversible stimulation of adenylate cyclase activity, and that persistence of this stimulation depends on the continuous presence of glucagon in the assay medium.

Journal ArticleDOI
TL;DR: The localization in situ of the low-density membrane subfraction on the surface of the hepatic cell is discussed, and it is suggested that it is derived mainly from the microvillar surface of hepatic parenchymal cells facing the perisinusoidal space.
Abstract: A procedure for the isolation and separation of three different subfractions of rat liver plasma membranes is described. The subfractions have different enzyme activities and sucrose buoyant densities of 1.18, 1.16 and 1.13 g/ml respectively. It was found that the low-density subfraction had the following properties: 1 It appeared as smooth membrane vesicles approximately 0.1–0.2 μm in diameter when visualized under positive and negative staining with the electron microscope. 2 Its contamination by microsomes on a protein basis was less than 3% as measured by glucose-6-phosphatase activity, and no succinic dehydrogenase activity or DNA were detected. 3 The low-density subfraction contained high relative specific activities of 5′-nucleotidase, (Na+, K+)-Mg2+-stimulated ATPase, phosphodiesterase, and a glucagon and adrenalin-sensitive adenylate cyclase. This fraction yielded over 30% of the total 5′-nucleotidase, adenylate cyclase and phosphodiesterase activities of the homogenate. 4 A specific 3′: 5′-AMP phosphodiesterase activity of this subfraction was stimulated by insulin. The half-maximal concentration required to produce this stimulation was 2.3 nM. The stimulation was already observed at the shortest time interval tested (30 sec). The localization in situ of the low-density membrane subfraction on the surface of the hepatic cell is discussed, and it is suggested that it is derived mainly from the microvillar surface of hepatic parenchymal cells facing the perisinusoidal space.

Journal ArticleDOI
TL;DR: It was concluded that adenyl cyclase seems not to be a normal constituent of brush borders, like NaK-ATPase, who are present in plasma membrane preparations derived largely from the basal and lateral margins of the epithelial cells, both may be phospholipid dependent enzymes and both are affected by cholera toxin.
Abstract: Brush borders and plasma membranes have been purified from mucosal epithelial cells of rabbit ileum under control conditions and after treatment for 3 hr with cholera toxin in vivo. The activity of several enzymes in these preparations was measured. It was concluded that adenyl cyclase, like NaK-ATPase, seems not to be a normal constituent of brush borders. Both these enzymes are present in plasma membrane preparations derived largely from the basal and lateral margins of the epithelial cells, both may be phospholipid dependent enzymes and both are affected by cholera toxin. Adenyl cyclase activity is increased while NaK-ATPase is decreased. The activities of alkaline phosphatase, leucineaminopeptidase, 5′-nucleotidase, glucose-6-phosphatase, and Mg-ATPase were not found to be affected by the toxin. Cholera toxin, which makes contact with the luminal side of the epithelial cells, in the natural disease and in the experimental model, would appear to exert its pathologic effect on adenyl cyclase at the opposite (basal and lateral) side of the cells.

Journal ArticleDOI
TL;DR: The results are consistent with the idea that 5-HT has two actions: one is to stimulate the enzyme adenyl cyclase to synthesize cyclic AMP, which, in turn, stimulates cation transport, and the other is to increase anion transport by a mechanism which is independent of cyclicAMP.
Abstract: 1. The role of cyclic AMP in mediating the action of 5-HT on salivary glands has been studied by measuring transepithelial potentials. 2. The lumen of unstimulated glands is 4 mV positive but becomes 12 mV negative after treatment with 5-HT (10 -8 M). Both the potential and the secretory responses to 5-HT are dose-dependent over the same concentration range. 3. The electrical response of salivary glands to cyclic AMP is qualitatively different to that of 5-HT; instead of going negative the potential goes more positive. 4. An increase in positive potential is also observed after treatment with theophylline (10 -2 M), or when glands are stimulated with 5-HT in a chloride-free saline. 5. These results are consistent with the idea that 5-HT has two actions. One is to stimulate the enzyme adenyl cyclase to synthesize cyclic AMP, which, in turn, stimulates cation transport. The other is to increase anion transport by a mechanism which is independent of cyclic AMP.

Journal ArticleDOI
TL;DR: Liver plasma membranes may be an important site for specific inactivation of glucagon, and a possible relationship between the glucagon inactivation process and the receptor for glucagon is discussed.

Journal ArticleDOI
TL;DR: Findings are presented that NSILA-S, a polypeptide with a similar molecular weight as insulin which is known to mimic most metabolic effects of the hormone could also inhibit the glucagon effect over a physiologically relevant concentration range, but had no effect upon the fluoride-stimulated system.

Journal ArticleDOI
TL;DR: The results suggest that calcium plays multiple regulatory roles with millimolar concentrations inhibiting binding to membrane receptor sites and lower calcium concentrations mediating at a locus within the membrane matrix between the receptor site and the site occupied by adenylate cyclase.

Journal ArticleDOI
TL;DR: Specific enzyme activity in enzyme preparations obtained from rats with free access to food and stimulated in vivo by secretin and pancreozymin is twice as high as that in enzymes preparations from starved animals.

Journal ArticleDOI
TL;DR: After incubation of platelets with either thrombin or L-PHA, there is an apparent 2-fold increase in the number of receptor sites for lentil-P HA, suggesting that these compounds produce a conformational change in the platelet surface exposing increased numbers of lentil -PHA receptor sites.

Journal ArticleDOI
TL;DR: Regression analysis shows a linear correlation between the percentage of adenyl-cyclase stimulation and the magnitude of changes of net water and sodium flux and this data strongly support the hypothesis thatadenyl cyclase is the mediator of the accumulation of intestinal fluid in cholera.
Abstract: Recent evidence suggests that the diarrheal effect of cholera enterotoxin is mediated by stimulation of intestinal adenyl cyclase and increased formation of intracellular adenosine 3' , 5' -cyclic monophosphate (cyclic AMP) This study demonstrates the stimulation of adenyl cyclase in canine jejunal mucosa by cholera toxin during experimental cholera Percentage increase of basal adenyl-cyclase activity correlates in time course and magnitude with simultaneously measured changes of net water and sodium fluxes Onset of enzyme activation and change of net water and sodium fluxes occur simultaneously between 30 and 60 min Maximal changes in activity of the enzyme and net movement of water and sodium also coincide at 150 and 180 min By 48 hr, the restoration of normal fluxes is accompanied by the return of enzymatic activity to baseline value Regression analysis shows a linear correlation between the percentage of adenyl-cyclase stimulation and the magnitude of changes of net water and sodium flux These data strongly support the hypothesis that adenyl cyclase is the mediator of the accumulation of intestinal fluid in cholera

Journal ArticleDOI
TL;DR: A correlation between compounds with pharmacological activity in vivo and inhibition of phosphodiesterase activity in vitro was indicated and classes of drugs active in the CNS appeared particularly active inThe in vitro systems investigated, as did antiparasitic agents.

Journal ArticleDOI
TL;DR: Purified liver plasma membranes isolated from adrenalectomized rats are characterized by a high sensitivity to glucagon and fluoride and an unusual sensitivity to epinephrine, thus allowing a comparative study of the two hormonal responses.

Journal ArticleDOI
TL;DR: These studies suggest strongly that adenyl cyclase is the mediator of the known effects of calcium ion on PTH secretion.

Journal ArticleDOI
TL;DR: It is suggested that β-ecdysone stimulates adenyl cyclase (and guanyl cyclase) but that the hormone also exerts effects on target cells independent of the cyclic AMP system.

Journal ArticleDOI
TL;DR: Lambdoid phages form clear plaques and show reduced ability to establish immunity in strains of Escherichia coli that lack adenylate cyclase or catabolite activator protein.
Abstract: Lambdoid phages form clear plaques and show reduced ability to establish immunity in strains of Escherichia coli that lack adenylate cyclase or catabolite activator protein. The absence of the activator protein or cyclic AMP reduces the frequency of lysogenization, but does not prevent steady-state repressor synthesis of a lysogen. Lambda phage mutants able to form turbid plaques on strains that lack catabolite activator protein or adenylate cyclase have been isolated and analyzed.