Effects of adenosine and adenosine-analogs on adenylate cyclase activity in the rat adipocyte plasma membrane: comparison of the properties of the enzyme with Mn2+ and Mg2+ as divalent cations

1981 ◽  
Vol 40 (2) ◽  
pp. 65-73 ◽  
Author(s):  
J. de Vente ◽  
J. Zaagsma
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Divalent Cations ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Adenosine Analogs

scholarly journals Ultrastructural localization of adenylate cyclase activity in chicken osteoclasts.

1991 ◽  
Vol 39 (9) ◽  
pp. 1207-1213 ◽  
Author(s):  
O Fukushima ◽  
T Yamamoto ◽  
C V Gay
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Cell Function ◽  
Ultrastructural Localization ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Marrow Cavity ◽  
Calcium Diet ◽  
Low Calcium Diet ◽  
Ruffled Border

Using lead citrate as a capture reagent and adenylate-(beta, gamma-methylene) diphosphate (AMP-PCP) as a substrate, we localized adenylate cyclase activity on the non-ruffled border plasma membrane of approximately half of the osteoclasts on trabecular bone surfaces in the tibial metaphyses of chickens fed a low (0.3%)-calcium diet. The enzyme was not detectable in osteoclasts when chickens were fed a normal calcium diet. Activity was observed on the entire plasma membrane of detached osteoclasts that were situated between osteoblasts on the bone surface and blood vessels in the marrow cavity. Detection of activity on detached osteoclasts required the presence of an activator, implying lower levels in these cells than in those with ruffled borders. Staining was greater on the lateral sides of osteoblasts and osteoclasts when they were in contact with each other. Reaction specificity was indicated by the demonstration of stimulation by forskolin, guanylate-(beta, gamma-methylene) diphosphate (GMP-PCP), dimethylsulfoxide, and NaF, inhibition by alloxan and 2',5'-dideoxyadenosine, and absence of activity when sections were incubated in substrate-free medium or when GMP-PCP replaced AMP-PCP as a substrate. The finding of adenylate cyclase in osteoclast plasma membrane provides structural evidence that the adenylate cyclase-cyclic AMP system has a role in regulation of osteoclast cell function. The low-calcium diet appears to have resulted in increased amounts of adenylate cyclase in osteoclasts.

scholarly journals Diet fat influences liver plasma-membrane lipid composition and glucagon-stimulated adenylate cyclase activity

1983 ◽  
Vol 212 (3) ◽  
pp. 573-583 ◽  
Author(s):  
P J Neelands ◽  
M T Clandinin
Keyword(s):  
Fatty Acid Composition ◽  
Plasma Membrane ◽  
Fatty Acid ◽  
Adenylate Cyclase ◽  
Acid Composition ◽  
Unsaturated Fatty Acid ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Fat Intake ◽  
Omega 6

Rats were fed diets that differed in fatty acid composition or in the proportion of energy derived from fat to determine if alteration of dietary fat intake influences the structural lipid composition of liver plasma membrane and the expression of an associated hormone-receptor-mediated function. Weanling rats were fed 9% (w/w) or 20% (w/w) low-erucic acid rape-seed oil or 9% (w/w) soya-bean oil for 24 days. Plasma membranes were isolated and the effect of diet fat on the fatty acid composition of phosphatidylcholine, phosphatidylethanolamine, phosphatidylserine, phosphatidylinositol and sphingomyelin was determined. Diet fat significantly altered total saturated and (omega-9) and (omega-6)-unsaturated fatty acid composition in addition to the (omega-6)- to (omega-3)-unsaturated fatty acid ratio in these polar lipids. Feeding the high-fat diet increased the (omega-6)- to (omega-3)-unsaturated fatty acid ratio and the (omega-9)-unsaturated fatty acid content in all lipids except sphingomyelin. Assay of glucagon-stimulated adenylate cyclase activity at both high and low glucagon concentrations indicated that high-fat intake also decreased cyclic AMP formation. In a second experiment the fat intake was held constant (40% of energy) and oleic acid was substituted for linoleic acid by blending high- and low-linoleic acid-type safflower oils. This experiment established that a dose-response relationship exists between dietary intake of fatty acid and the fatty acid composition of plasma-membrane phospholipids. Specific diet-induced transitions in membrane phospholipid fatty acid composition were paralleled by changes in glucagon-stimulated adenylate cyclase activity. This study suggests that transitions in dietary fat intake can alter a hormone-receptor-mediated enzyme function in vivo by changing the surrounding lipid environment.

scholarly journals N 6-(Phenylisopropyl)adenosine prevents glucagon both blocking insulin's activation of the plasma-membrane cyclic AMP phosphodiesterase and uncoupling hormonal stimulation of adenylate cyclase activity in hepatocytes

1984 ◽  
Vol 222 (1) ◽  
pp. 177-182 ◽  
Author(s):  
A V Wallace ◽  
C M Heyworth ◽  
M D Houslay
Keyword(s):  
Plasma Membrane ◽  
Cyclic Amp ◽  
Adenylate Cyclase ◽  
Phosphodiesterase Inhibitor ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Maximal Effect ◽  
Hormonal Stimulation ◽  
Cyclic Amp Phosphodiesterase ◽  
Phenylisopropyl Adenosine

Glucagon (10nM) prevented insulin (10nM) from activating the plasma-membrane cyclic AMP phosphodiesterase. This effect of glucagon was abolished by either PIA [N6-(phenylisopropyl)adenosine] (100nM) or adenosine (10 microM). Neither PIA nor adenosine exerted any effect on the plasma-membrane cyclic AMP phosphodiesterase activity either alone or in combination with glucagon. Furthermore, PIA and adenosine did not potentiate the action of insulin in activating this enzyme. 2-Deoxy-adenosine (10 microM) was ineffective in mimicking the action of adenosine. The effect of PIA in preventing the blockade by glucagon of insulin's action was inhibited by low concentrations of theophylline. Half-maximal effects of PIA were elicited at around 6nM-PIA. It is suggested that adenosine is exerting its effects on this system through an R-type receptor. This receptor does not appear to be directly coupled to adenylate cyclase, however, as PIA did not affect either the activity of adenylate cyclase or intracellular cyclic AMP concentrations. Insulin's activation of the plasma-membrane cyclic AMP phosphodiesterase, in the presence of both glucagon and PIA, was augmented by increasing intracellular cyclic AMP concentrations with either dibutyryl cyclic AMP or the cyclic AMP phosphodiesterase inhibitor Ro-20-1724. PIA also inhibited the ability of glucagon to uncouple (desensitize) adenylate cyclase activity in intact hepatocytes. This occurred at a half-maximal concentration of around 3 microM-PIA. However, if insulin (10 nM) was also present in the incubation medium, PIA exerted its action at a much lower concentration, with a half-maximal effect occurring at around 4 nM.

Adenylate cyclase activity in Y1 mouse adrenocortical tumor cells: some properties of the enzyme associated with purified plasma membrane fractions

1983 ◽  
Vol 61 (7) ◽  
pp. 547-552 ◽  
Author(s):  
Bernard P. Schimmer
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Plasma Membranes ◽  
Tumor Cell Line ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Adenylate Cyclase System ◽  
Adrenocortical Tumor ◽  
Intact Cells ◽  
Order Of Magnitude

Fractions enriched in plasma membranes were prepared from the Y1 mouse adrenocortical tumor cell line and were characterized with respect to adenylate cyclase activity. Optimal requirements of the adenylate cyclase system for guanyl nucleotides, Mg2+, ATP, and corticotropin (ACTH) were determined. The sensitivity of the adenylate cyclase system to ACTH1–24 in plasma membrane fractions was comparable with that observed in isolated intact cells. Polycations such as poly-L-arginine and histone competitively inhibited the action of ACTH1–24, supporting the view that the affinity of ACTH for the adenylate cyclase system is determined by the basic core of amino acids at residues 15–18. ACTH1–24 was at least one order of magnitude more potent than ACTH1–39 in stimulating adenylate cyclase activity in plasma membrane fractions.

scholarly journals Adenylate cyclase activity in lymphocyte subcellular fractions. Characterization of non-nuclear adenylate cyclase

1977 ◽  
Vol 162 (3) ◽  
pp. 473-482 ◽  
Author(s):  
D E Snider ◽  
C W Parker
Keyword(s):  
Enzyme Activity ◽  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Prostaglandin E1 ◽  
Plasma Membranes ◽  
Subcellular Fractions ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Marker Enzyme ◽  
Discontinuous Sucrose Gradient

Human peripheral lymphocytes were broken in a Dounce homogenizer and subcellular fractions enriched in plasma membranes or microsomal particles and mitochondria were isolated by centrifugation through a discontinuous sucrose gradient. Various agents that promote cyclic AMP accumulation in intact lymphocytes were compared in their ability to stimulate adenylate cyclase activity in the individual fractions. Plasma-membrane-rich fractions that were essentially free of other subcellular particles as judged by electron microscopy and marker enzyme measurements responded to fluoride, but weakly or not at all to prostaglandin E1 and other prostaglandins. Microsomal and mitochondrial-rich fractions responded markedly to both prostaglandin E1 and fluoride. In some, but not all, experiments phytohaemagglutinin produced a modest increase in enzyme activity in plasma-membrane-rich fractions. Catecholamines, histamine, parathyrin, glucagon and corticotropin produced little or no response. In the absence of theophylline, adenosine (1-10 micronM) stimulated basal enzyme activity, although at higher concentrations the responses to prostaglandin E1 and fluoride were inhibited. GTP (1-100 micronM) and GMP(5-1000 micronM) respectively inhibited or stimulated the response to fluoride, whereas the converse was true with prostaglandin E1.

scholarly journals Modulation of the response of bovine adrenocortical adenylate cyclase to corticotropin

1977 ◽  
Vol 168 (2) ◽  
pp. 277-282 ◽  
Author(s):  
P Glynn ◽  
D M F Cooper ◽  
D Schulster
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Guanine Nucleotide ◽  
Half Maximum ◽  
Basic Parameters ◽  
High Concentrations ◽  
Plasma Membrane Preparation ◽  
Stimulation Of

An assessment was made of some of the basic parameters responsible for the modulation of adenylate cyclase activity in a bovine adrenocortical plasma-membrane preparation. When determined at 0.1 mM-ATP, basal adenylate cyclase activity increased with increasing MgCl2 concentrations, whereas in the presence of corticotropin activity was essentially maximal at 10mM-MgCl2; high concentrations (25mM) of MgCl2 inhibited adenylate cyclase activity determined in the presence of both corticotropin and GTP. At all MgCl2 concentrations, corticotropin and GTP activated the enzyme in a synergistic fashion. The magnitude of the stimulation of basal activity produced by corticotropin was a function of Mg2+ concentration, whereas that produced by GTP appeared largely independent of Mg2+ concentration. Adenylate cyclase activity in the bovine adrenal membrane was half-maximally stimulated by corticotropin concentrations in the range 0.3—1.0 nM. The concentration of corticotropin evoking half-maximum response was not significantly affected by raising the free Mg2+ concentration from 0.4 to 4.9 mM, nor by the presence of GTP. In the presence of GTP, high concentrations (over 1 micrometer) of corticotropin inhibited adenylate cyclase activity, although no inhibition was apparent in the absence of guanine nucleotide.

scholarly journals Functional polarity of the rat hepatocyte surface membrane. Isolation and characterization of plasma-membrane subfractions from the blood-sinusoidal, bile-Canalicular and contiguous surfaces of the hepatocyte

1975 ◽  
Vol 146 (2) ◽  
pp. 375-388 ◽  
Author(s):  
M H Wisher ◽  
W H Evans
Keyword(s):  
Plasma Membrane ◽  
Adenylate Cyclase ◽  
Gradient Centrifugation ◽  
Polyacrylamide Gel Electrophoresis ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Morphological Properties ◽  
Differential Rate ◽  
Marker Enzymes ◽  
Isolation And Characterization

1. Six rat liver plasma-membrane subfractions of different density and morphological, enzymic and chemical properties were prepared from homogenates by a combination of differential, rate-zonal and density-gradient centrifugation. They consisted of three vesicular ‘light’ subfractions of density 1.12-1.13 and three ‘heavy’ subfractions of density 1.16-1.18 containing membrane strips and intercellular junctions. 2. All six subfractions contained a basal adenylate cyclase activity. One of the ‘light’ subfractions that showed the highest glucagon-stimulated adenylate cyclase activity was identified as deriving form the blood-sinusoidal face of the hepatocyte. This subfraction, unlike the others, was contaminated by Golgi components, as indicated by its morphological properties and the presence of galactosyl- and sialyl-transferase activities. 3. All the six subfractions showed high activities of the following plasma-membrane marker enzymes: 5′-nucleotidase, alkaline phosphodiesterase (nucleotide pyrophosphatase), alkaline phosphatase, leucine naphthylamidase and Mg2+-activated adenosine triphosphatase. A ‘light’ subfraction that showed the highest specific activities of all the above marker enzymes, but lacked a glucagon-stimulated adenylate cyclase activity, was identified as deriving from the bile-canalicular face of the hepatocyte. 4. The ‘heavy’ subfractions, which showed generally the lowest activities of the above plasma-membrane enzyme markers, and were characterized by the presence of desmosomes and gap junctions, were taken to originate from the contiguous faces of the hepatocyte. 5. The protein composition of the six subfractions was generally similar, as shown by polyacrylamide-gel electrophoresis. Differences in the amounts of various protein and glycoprotein bands among the subfractions correlated with their morphology, enzymic composition and sialic acid content. 6. Hormonal and histochemical evidence supporting the identification of a bile-canalicular subfraction, a blood-sinusoidal subfraction and contiguous-face subfractions is discussed.

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