scholarly journals Inhibition of adenylate cyclase in rat brain synaptosomal membranes by GTP and phenylisopropyladenosine is enhanced in hypothyroidism

1989 ◽  
Vol 263 (3) ◽  
pp. 829-835 ◽  
Author(s):  
D Mazurkiewicz ◽  
E D Saggerson
Keyword(s):  
Adenylate Cyclase ◽  
Rat Brain ◽  
Adenosine Receptor ◽  
Receptor Agonist ◽  
Adenylate Cyclase System ◽  
Synaptosomal Membranes ◽  
A1 Adenosine Receptor ◽  
Adenosine Receptor Agonist ◽  
Coupling Protein ◽  
The Brain

1. Synaptosomal membranes were isolated from rats made hypothyroid by treatment with propylthiouracil and a low iodine diet. 2. When assayed in the presence of 100 mM-Na+, inhibition of forskolin-stimulated adenylate cyclase by GTP was enhanced in membranes from hypothyroid animals. 3. Hypothyroidism also enhanced inhibition of adenylate cyclase by phenylisopropyladenosine (with 100 mM-Na+ and 10 microM-GTP present). 4. Hypothyroidism did not increase binding of the A1 adenosine receptor agonist phenylisopropyladenosine to synaptosomal membranes; rather, the maximum binding was slightly decreased without any change in the KD. 5. The effect of GTP in modifying the displacement of the antagonist [3H]diethylphenylxanthine from synaptosomal membranes by unlabelled phenylisopropyladenosine was more pronounced in the hypothyroid state. 6. These findings are consistent with hypothyroidism causing modification of the brain adenylate cyclase system at the level of the coupling protein Gi.

Evidence for regulated coupling of A1 adenosine receptors by phosphorylation in Zucker rats

1995 ◽  
Vol 268 (4) ◽  
pp. E693-E704 ◽  
Author(s):  
D. A. Berkich ◽  
D. R. Luthin ◽  
R. L. Woodard ◽  
S. J. Vannucci ◽  
J. Linden ◽  
...  
Keyword(s):  
Adenosine Receptor ◽  
Adenosine Receptors ◽  
Receptor Agonist ◽  
High Sensitivity ◽  
Zucker Rats ◽  
Guanine Nucleotide ◽  
Agonist Binding ◽  
A1 Adenosine Receptor ◽  
Adenosine Receptor Agonist ◽  
A1 Adenosine Receptors

Studies were designed to find the molecular basis for previous observations that lipolysis is less active and A1 adenosine receptor signaling is more active in adipocytes from obese than from lean Zucker rats. With quantitative immunoblot procedures for detection, Gi alpha 1 and Gs alpha 45 levels were found anomalously low in obese compared with lean membranes (50 and 30%, respectively), but other G alpha subunit levels were normal. However, the sensitivity of the receptor-Gi protein to GTP was about 5- to 10-fold higher in obese compared with lean membranes when assessed from 1) the ability of GTP to inhibit forskolin-stimulated adenylyl cyclase in the presence of an adenosine receptor agonist and 2) the ability of a nonhydrolyzable guanine nucleotide analogue to alter A1 adenosine receptor agonist binding. Alkaline phosphatase treatment of isolated adipocyte membranes from obese but not lean animals decreased guanine nucleotide sensitivity of agonist binding. Surprisingly, solubilized adipocyte A1 adenosine receptors from all animals exhibited the same high sensitivity to guanine nucleotides as that of intact obese membranes, and this high sensitivity could be decreased 20-fold by treatment with alkaline phosphatase. These data suggest that protein phosphorylation may regulate coupling of the A1 adenosine receptor in rat adipocyte membranes.

scholarly journals Circannual Rhythm in Body Temperature, Torpor, and Sensitivity to A1 Adenosine Receptor Agonist in Arctic Ground Squirrels

2013 ◽  
Vol 28 (3) ◽  
pp. 201-207 ◽  
Author(s):  
Jasmine M. Olson ◽  
Tulasi R. Jinka ◽  
Lindy K. Larson ◽  
Jeffrey J. Danielson ◽  
Jeanette T. Moore ◽  
...  
Keyword(s):  
Body Temperature ◽  
Adenosine Receptor ◽  
Receptor Agonist ◽  
Ground Squirrels ◽  
Circannual Rhythm ◽  
A1 Adenosine Receptor ◽  
Adenosine Receptor Agonist ◽  
Arctic Ground Squirrels

Adenosine receptor coupling to adenylate cyclase of rat ventricular myocyte membranes

1989 ◽  
Vol 257 (4) ◽  
pp. H1088-H1095 ◽  
Author(s):  
F. D. Romano ◽  
S. G. MacDonald ◽  
J. G. Dobson
Keyword(s):  
Adenylate Cyclase ◽  
Adenosine Receptor ◽  
Adrenergic Receptor ◽  
Receptor Agonist ◽  
Cyclase Activity ◽  
Adenylate Cyclase Activity ◽  
Ventricular Myocyte ◽  
Beta Adrenergic Receptor ◽  
Beta Adrenergic ◽  
Adenosine Receptor Agonist

The effects of adenosine analogues on beta-adrenergic receptor and receptor-independent elicited increases in adenylate cyclase activity were investigated using membranes obtained from primary cultures of adult rat ventricular myocytes. Phenylisopropyladenosine, an A1-receptor agonist, at concentrations of 0.1, 1.0, and 10 microM, maximally inhibited isoproterenol-stimulated adenylate cyclase activity by 35, 55, and 41%, respectively. The inhibition by phenylisopropyladenosine was antagonized by 10 microM theophylline. One micromolar phenylisopropyladenosine was much less effective at attenuating forskolin-stimulated activity, such that the maximum inhibition was 26%. Phenylisopropyladenosine had no effect on adenylate cyclase stimulation by 5'-guanylylimidodiphosphate. Phenylaminoadenosine, an A2 agonist, at 10 microM or greater stimulated adenylate cyclase activity. This effect was not significantly inhibited by theophylline or 0.1 microM 1,3-dipropyl-8-cyclopentylxanthine (DPCPX), which antagonized phenylisopropyladenosine inhibition of isoproterenol-stimulated adenylate cyclase activity. Additionally, N-ethylcarboxamidoadenosine, a nonselective adenosine-receptor agonist, had no effect on adenylate cyclase activity in the absence of DPCPX but stimulated adenylate cyclase activity in the presence of DPCPX. These results indicate that both A1 and A2 receptors exist on the ventricular myocyte sarcolemma. More importantly, the findings suggest that adenosine inhibition of catecholamine-stimulated adenylate cyclase activity is primarily due to an alteration in beta-adrenergic receptor-mediated transduction and perhaps in part by a direct inhibition of the catalytic component.

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