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

---

Query: KEGG:D06103 (Theophylline)
2,023 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Dilazep (i.p.), a coronary vasodilator and an uptake inhibitor of adenosine, dose dependently potentiated acute ethanol-induced motor incoordination in mice. In view of peripheral cardiovascular depressive effects of dilazep, the effect of i.c.v. dilazep (25, 50 and 75 micrograms), and its metabolites, 1,4-bis(3-hydroxypropyl)perhydro-1,4-diazepine (BHPD) (15, 31 and 62 micrograms) and 1-[3-(3,4,5-trimethoxybenzoyloxy)propyl]perhydro-1,4-diazepine (TBPD) (62 and 125 micrograms) on ethanol-induced motor incoordination was studied. Dose-related potentiation of ethanol-induced motor incoordination was noted with dilazep and its metabolites. Whereas dilazep (i.p.) produced no apparent central nervous system (CNS) effects, by i.c.v. route, it caused CNS excitation including tonic-clonic seizures. Adenosine uptake inhibition, Ca2+ entry blockade or direct activation of adenosine receptors was ruled out as the possible mechanism of seizures because dipyridamole, verapamil or N6-(2-phenylisopropyl)-adenosine (R-PIA) administered i.c.v., while potentiating ethanol (i.p.)-induced motor incoordination did not produce seizures. The CNS excitation was minimal with BHPD and none with TBPD. Theophylline pretreatment partially blocked potentiation of ethanol-induced motor incoordination by dilazep and BHPD and not by TBPD. The data suggest dilazep-induced potentiation of ethanol-induced motor incoordination is partially due to central adenosine receptor mechanism and partly due to other yet unknown mechanism(s) and further supported our earlier reports about adenosine involvement in the CNS effects of ethanol. The data also suggest that dilazep (i.c.v.)-induced seizures are due to mechanism(s) other than adenosine uptake inhibition, Ca2+ entry blockade or direct adenosine receptor activation.
...
PMID:Central nervous system effects and behavioral interactions with ethanol of centrally administered dilazep and its metabolites in mice. 275 78

125I-Hydroxyphenylisopropyl adenosine (125I-HPIA) was used to characterize adenosine receptors in human adipocyte plasma membranes. Steady state binding was achieved after 6 h at 37 degrees. Scatchard plots were linear, with a KD of approx. 2.5 nM, and Bmax of 360-1800 fmol/mg protein. (-)N6-phenylisopropyl adenosine (PIA) was a more potent inhibitor of binding than N-ethyl carboxamido adenosine, and (+)PIA was more than 10-fold less potent than (-)PIA, consistent with A1 adenosine receptor binding. Theophylline was a potent inhibitor of binding (IC50 approx. 10 microM). Photoaffinity cross-linking studies demonstrated that the receptor is a single subunit, Mr approx. 43 kDa. The findings demonstrate that the human adipocyte adenosine receptor is similar to the A1 adenosine receptor of rat adipocytes, although its molecular weight is higher, and its affinity for HPIA is lower than that of the rat.
...
PMID:Characterization of human adipocyte adenosine receptors. 277 54

Hormonal regulation of Mg2+ influx was examined in the neuroblastoma X glioma hybrid cell line NG108-15 and the skeletal muscle cell line G8 using 28Mg2+. Both cell lines express multiple classes of hormone receptors; in addition, G8 cells can be induced to differentiate from a single myoblast-like cell into fused myotube-like cells. In NG108-15 cells, 2-Cl-adenosine, an adenosine receptor agonist, stimulated Mg2+ influx by about 60%. This effect was not mimicked by norepinephrine or PGE1, agonists at alpha 2-adrenergic and prostaglandin receptors which NG108-15 cells also express. Carbachol, acting through a muscarinic receptor, gave minimal and variable stimulation of Mg2+ influx. The effect of 2-Cl-adenosine was not blocked by theophylline, an adenosine receptor antagonist, and was not mimicked by adenosine analogs selective for either A1 or A2 adenosine receptors, suggesting that a nonclassical adenosine receptor mediates the effect on Mg2+ influx. Theophylline slightly stimulated Mg2+ influx as did the permeable cyclic AMP analog, 8-Br-cyclic AMP. These results indicate that cyclic AMP may influence Mg2+ influx in NG108-15 cells unlike previous results in murine S49 lymphoma cells [Maguire and Erdos, J. biol. Chem. 255: 1030-1035, 1980] where receptor modulation of Mg2+ influx was independent of cyclic AMP. In G8 cells, the nicotinic cholinergic receptor agonist carbachol stimulated Mg2+ influx at the myoblast cell stage but had no effect on Mg2+ influx after cells had formed myotubes. The beta-adrenergic agonist isoproterenol had the opposite effect, stimulating Mg2+ influx in the myotube stage but not in the myoblast stage. Taken together, these results demonstrate that only a subset of receptors expressed by a cell may be coupled to Mg2+ influx, that the regulation of Mg2+ influx differs from cell type to cell type, and finally, that modulation of Mg2+ influx by hormone receptors may change with differentiation.
...
PMID:Hormonal regulation of magnesium uptake: differential coupling of membrane receptors to magnesium uptake. 282 11

Previous studies by others have demonstrated that exogenous adenosine inhibits renin secretion in vivo. In the present experiments, we studied the effects of three adenosine receptor agonists [N6-cyclohexyladenosine (CHA), 2-chloroadenosine (2-CIA) and 5'-N-ethylcarboxamideadenosine (NECA)] on renin secretion of rat renal cortical slices. The effects were biphasic; submicromolar concentrations inhibited secretion concentration-dependently and the order of potency was CHA greater than 2-CIA greater than NECA. Micromolar and higher concentrations stimulated secretion concentration-dependently and the order of potency was reversed: NECA greater than 2-CIA greater than CHA. These results are consistent with the hypothesis that activation of A1 and A2 adenosine receptors produces inhibition and stimulation of secretion, respectively. Theophylline antagonized both the inhibitory effect of low concentrations of CHA and the stimulatory effect of higher concentrations, providing additional evidence for mediation by activation of cell-surface adenosine receptors. Calcium chelation abolished the inhibitory effect of CHA, suggesting that increased intracellular calcium mediates the inhibitory effect; on the other hand, the inhibitory effect was unaffected by membrane depolarization and calcium channel blockade, suggesting that CHA-induced inhibition is not due to calcium influx through voltage-sensitive calcium channels. Ouabain, vanadate and K-depolarization, all of which are believed to increase intracellular calcium, antagonized CHA- and NECA-stimulated renin secretion, suggesting that the stimulatory effect of these agonists is mediated by decreased intracellular calcium.(ABSTRACT TRUNCATED AT 250 WORDS)
...
PMID:A1 and A2 adenosine receptor activation inhibits and stimulates renin secretion of rat renal cortical slices. 298 63

A series of 8-(substituted phenyl) derivatives of theophylline and other 1,3-dialkylxanthines were evaluated for potency and selectivity as antagonists at A1- and A2-adenosine receptors in brain tissue. Theophylline has a similar potency (Ki = 14 microM) at both A1 and A2 receptors. 8-Phenyltheophylline is 25-35-fold more potent as an adenosine receptor antagonist than theophylline, while 8-phenylcaffeine is only 2-3-fold more potent than caffeine. A p-hydroxyaryl substituent enhances the potency of 8-phenyltheophylline as an adenosine antagonist. p-Carboxy- and p-sulfoaryl substituents reduce potency of 8-phenyltheophylline, yielding water-soluble adenosine antagonists, which are some 2-5-fold more potent than theophylline at adenosine receptors. None of the 8-(substituted phenyl)theophyllines are particularly selective as antagonists toward A1- and A2-adenosine receptors. 1,3-Dipropyl-8-phenylxanthine represents a potent and somewhat selective A1-receptor antagonist about 23-fold more potent at A1 receptors than at A2 receptors. A p-hydroxyaryl substituent further enhances potency of the 1,3-dipropyl-8-phenylxanthine at both A1 and A2 receptors. The 8-(2-amino-4-chlorophenyl)-1,3-dipropylxanthine is a very potent and selective antagonist for A1 receptors, being nearly 400-fold more potent at A1 than at A2 receptors. The water-soluble 8-(p-sulfophenyl)- and 8-(p-carboxyphenyl)-1,3-propylxanthines no longer exhibit marked selectivity. Both compounds are much more potent as adenosine antagonists than theophylline. The striking selectivity of 1-isoamyl-3-isobutylxanthine as an A1 antagonist is retained in the 8-phenyl derivative but is virtually lost in the 8-p-sulfophenyl derivative.
...
PMID:1,3-Dialkyl-8-(p-sulfophenyl)xanthines: potent water-soluble antagonists for A1- and A2-adenosine receptors. 298 20

The effects of adenosine, the Ri site adenosine receptor agonist (-)-N6-phenylisopropyladenosine (PIA), the Ra site agonist 5'-N-ethylcarboxamideadenosine (NECA) and the P site agonist 2',5'-dideoxyadenosine (DIDA) on force of contraction, cyclic AMP (cAMP) and cyclic GMP (cGMP) content and on transmembrane action potential were studied in isolated electrically driven left auricles and papillary muscles from guinea pigs. Furthermore, the effects on adenylate cyclase activity in a particulate membrane preparation were investigated. In the auricles, adenosine, PIA and NECA had negative inotropic effects which were accompanied by a shortening of the action potential. Theophylline antagonized these effects which are likely mediated by R site adenosine receptors. DIDA was ineffective. Except for a small positive inotropic effect of adenosine the analogs were ineffective in the papillary muscles. None of the mechanical effects was accompanied by a change in cAMP and cGMP content in the intact preparations. In the broken cell preparation PIA and NECA had no effect on adenylate cyclase activity. Adenosine and DIDA inhibited the enzyme. The latter effects can be classified as P site-mediated effects. In conclusion, distinct mechanical, i.e., negative inotropic effects of adenosine and its analogs in the heart are observed in auricular preparations only. These effects are unlikely to be related to the cAMP and/or cGMP system. Instead, they are probably due to a direct shortening of the action potential which, in turn, is conceivably due to an increase in K+ outward current and a secondary decrease in Ca++ inward current. This effect is apparently mediated by cardiac R site adenosine receptors which are not detectably coupled to adenylate cyclase.
...
PMID:Cardiac effects of adenosine and adenosine analogs in guinea-pig atrial and ventricular preparations: evidence against a role of cyclic AMP and cyclic GMP. 299 94

The effects of adenosine receptor agonists and antagonists were examined in epithelia formed in culture by A6 cells, a continuous cell line derived from Xenopus laevis kidney. A6 epithelia have a high electrical resistance and a short-circuit current that is equal to net sodium flux from mucosal to serosal surface. Adenosine, 2-chloroadenosine, 5'-(N-ethyl)carboxamidoadenosine, and N6-(L-2-phenylisopropyl) adenosine produced concentration-dependent increases in short-circuit current. Stimulation of short-circuit current by 2-chloroadenosine occurred at concentrations of 0.05 microM and above, with half-maximal stimulation occurring at 0.3 microM. 5'-(N-ethyl)carboxamidoadenosine was more potent than N6-(L-2-phenylisopropyl)adenosine, the usual order of potency for activation of stimulatory adenosine receptors. Theophylline (100 microM), an adenosine receptor antagonist, reduced the short-circuit current response to adenosine and 2-chloroadenosine by 85-90%. Amiloride, an agent that inhibits both basal and adenosine 3',5'-cyclic monophosphate (cAMP)-stimulated short-circuit current in A6 epithelia, completely and reversibly inhibited short-circuit current stimulated by 2-chloroadenosine. Adenosine and 2-chloroadenosine stimulated adenylate cyclase activity in a crude membrane preparation from A6 cells. Stimulation by adenosine was blocked by adenosine deaminase. 2-Chloroadenosine increased cell cAMP accumulation in intact epithelia. The results provide evidence that adenosine and adenosine receptor agonists stimulate adenylate cyclase and active sodium transport in an epithelial cell line of renal origin.
...
PMID:Adenosine stimulates sodium transport in kidney A6 epithelia in culture. 299 88

The effects of a 5'-substituted analogue of adenosine, 5'-N-ethylcarboxamidoadenosine (NECA) have been studied on glucagon secretion in vitro, using the isolated pancreas of the rat perfused in the presence of glucose (2.8 mM). NECA provoked a peak of glucagon secretion, the kinetics of which were comparable to those previously obtained with adenosine. The effect was concentration-dependent and appeared at nanomolar concentrations. The EC50 was approximately 4 X 10(-8) M. A comparison of relative potency between adenosine and NECA showed that NECA was about 800 fold more potent than adenosine in inducing glucagon secretion. Theophylline (50 microM) considerably decreased the peak of glucagon secretion induced by 1.65 microM NECA and totally suppressed the effect of 16.5 nM NECA. These results indicate the involvement of an adenosine receptor. These and other previous results (low stereoselectivity of N6-phenylisopropyladenosine) provide evidence for an adenosine receptor of the A2-subtype being involved in glucagon secretion.
...
PMID:Evidence for an A2-subtype adenosine receptor on pancreatic glucagon secreting cells. 299 22

The tricyclic anticonvulsant carbamazepine (CBZ) is effective in pain and affective disorder, but the mechanism of action for this drug has not been defined. Recently it was reported that CBZ had interaction with adenosine receptor, which is related to the inhibition of release of neurotransmitter. In the present study, we investigated the in vitro effects of CBZ and other drugs upon adenosine receptor binding using 3H-L-phenylisopropyladenosine (A1) and 3H-N-ethylcarboxamidoadenosine (A2). The following results were obtained: CBZ and its derivative oxcarbazepine inhibit 3H-PIA binding at therapeutic plasma level (20-30 microM) more than they inhibit 3H-NECA binding; Theophylline and caffeine, methylxanthines, which are adenosine antagonists, inhibit both bindings; Other anticonvulsants such as phenobarbital, phenytoin and valproate and still other psychotropic drugs such as diazepam, imipramine and chlorpromazine have little or no effect on both bindings. These findings suggest that anticonvulsive and sedative effects of CBZ and its derivatives appear due to action on adenosine receptors (A1 and partially A2) at the therapeutic level and methylxanthines have stimulant and convulsant effects due to occupation on both A1 and A2 adenosine receptors.
...
PMID:Interaction of carbamazepine and other drugs with adenosine (A1 and A2) receptors. 309 20

Upregulation of brain adenosine receptors in DBA/2J mice as affected by theophylline and caffeine, adenosine antagonists, was examined following subcutaneous drug implantation to ensure chronic exposure. Scatchard analysis of binding to membranes of cerebral cortex and cerebellum from individual mice showed a differential upregulation of (-)-N6-R-[G-3H]phenylisopropyladenosine ([3H]-L-PIA) binding density by theophylline. After 14 days of exposure to theophylline (serum concentration of 1.2 +/- 0.01 micrograms/ml measured by HPLC analysis), the Bmax for L-PIA binding to cerebellar membranes increased 22% over the control mice (statistically significant at P less than 0.01 level). Theophylline had no effect on the Bmax for L-PIA binding to cerebral cortical membranes. The observed increases in Bmax values of cerebellar (13.2%) and cerebral cortical membrane binding (14.2%) on chronic exposure to caffeine (7.1 +/- 0.5 micrograms/ml) were not statistically significant at the P less than or equal to 0.05 level. Neither methylxanthine affected the dissociation constant, KD, for L-PIA. The increased potential for adenosine receptor upregulation by theophylline compared to caffeine following chronic, low level exposure suggests that caffeine treatment for sleep apnea may be preferred to the standard theophylline therapy.
...
PMID:Chronic exposure to subcutaneously implanted methylxanthines. Differential elevation of A1-adenosine receptors in mouse cerebellar and cerebral cortical membranes. 360 53


<< Previous 1 2 3 4 5 6 7 8 9 Next >>

---