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Homo- and heteroexchange of adenine nucleotides and nucleosides in rat hippocampal slices by the nucleoside transport system.

ABSTRACT: (1) Here, we investigated how nucleotides and nucleosides affect the release of tritiated purines and endogenous adenosine 5'-triphosphate (ATP) from superfused rat hippocampal slices. (2) ATP elicited concentration-dependent [(3)H]purine efflux from slices preloaded with [(3)H]adenosine. High-performance liquid chromatography analysis of the effluent showed that the tritium label represented the whole set of adenine nucleotides and nucleosides, and ATP significantly increased the outflow of [(3)H]ATP. (3) Adenosine 5'-diphosphate, adenosine, uridine, uridine 5'-triphosphate, alpha,beta-methylene-ATP and 3'-O-(4-benzoylbenzoyl)-ATP were also active in eliciting [(3)H]purine release. Adenosine (300 micro M) also evoked endogenous ATP efflux from the hippocampal slices. (4) Reverse transcription-coupled-polymerase chain reaction analysis revealed that mRNAs encoding a variety of P2X and P2Y receptor proteins are expressed in the rat hippocampus. Nevertheless, neither P2 receptor (i.e. pyridoxal-5-phosphate-6-azophenyl-2',4'-disulphonic acid, 30 micro M, suramin, 300 micro M and reactive blue 2, 10 micro M), nor adenosine receptor (8-cyclopentyl-1,3-dipropylxanthine, 250 nM and dimethyl-1-propargylxanthine, 250 nM) antagonists modified the effect of ATP (300 micro M) to evoke [(3)H]purine release. (5) The nucleoside transport inhibitors, dipyridamole (10 micro M), nitrobenzylthioinosine (10 micro M) and adenosine deaminase (2-10 U ml(-1)), but not the ecto-adenylate kinase inhibitor diadenosine pentaphosphate (200 micro M) significantly reduced ATP-evoked [(3)H]purine efflux. (6) In summary, we found that ATP and other nucleotides and nucleosides promote the release of one another and themselves by the nucleoside transport system. This action could have relevance during physiological and pathological elevation of extracellular purine levels high enough to reverse the nucleoside transporter.

SUBMITTER: Sperlagh B

PROVIDER: S-EPMC1573884 | biostudies-literature | 2003 Jun

REPOSITORIES: biostudies-literature

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Homo- and heteroexchange of adenine nucleotides and nucleosides in rat hippocampal slices by the nucleoside transport system.

Sperlágh Beáta B Szabó Gábor G Erdélyi Ferenc F Baranyi Mária M Vizi E Sylvester ES

British journal of pharmacology 20030601 3

(1) Here, we investigated how nucleotides and nucleosides affect the release of tritiated purines and endogenous adenosine 5'-triphosphate (ATP) from superfused rat hippocampal slices. (2) ATP elicited concentration-dependent [(3)H]purine efflux from slices preloaded with [(3)H]adenosine. High-performance liquid chromatography analysis of the effluent showed that the tritium label represented the whole set of adenine nucleotides and nucleosides, and ATP significantly increased the outflow of [(3 ...[more]

PMID: 12788822

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Project description:1. The aim of this study was to investigate the effects of adenine nucleosides and nucleotides on contractility of the smooth muscle of rat prostate gland. 2. Nerve terminals within rat isolated prostatic tissues were electrically field stimulated (60 V, 0.5 ms, 10 Hz, 20 pulses every 60 s). Adenosine 5'-triphosphate (ATP), adenosine 5'-diphosphate (ADP), adenosine 5'-monophosphate (AMP) and adenosine had no effect on baseline smooth muscle tone but concentration-dependently inhibited electrically-evoked contractile responses. The relative order of potency was ATP congruent with AMP congruent with adenosine>ADP. 3. The inhibition by ATP and adenosine of field stimulation-induced contractions in the rat prostate was antagonized by 8-phenyltheophylline (10 microM), but not by suramin (100 microM) and only slightly by reactive blue 2 (5 microM). 4. The adenosine metabolizing enzyme adenosine deaminase (0.1 unit ml(-1)) inhibited the inhibitory effects of ATP and adenosine. The P2 purinoceptor agonist 2-methylthio ATP (10 nM - 0.1 mM), had no effect on field stimulation-induced contractions of the rat prostate. 5. ATP and adenosine did not modify the contractile responses of the rat prostate to exogenously added noradrenaline (10 microM). 6. Inhibitory concentration-response curves to a number of adenosine analogues with differing stabilities and selectivities for the different adenosine receptors yielded a relative rank order of agonist potency of: N(6)-cyclopentyladenosine (CPA)>N(6)-cyclohexyladenosine (CHA) congruent with (-)-N(6)-(2-phenylisopropyl)-adenosine (R-PIA) congruent with 5'-(N-ethylcarboxamido)-adenosine (NECA)>(+)-N(6)-(2-phenylisopropyl)-adenosine (S-PIA)>2-p-[2-carboxyethyl]phenethyl-amino-5'-N-ethylcarboxamido-ade nosine (CGS 21680). 7. These results indicate that adenine nucleoside and nucleotide induced inhibition of electrically-evoked contractions in the rat prostate occurs through activation of adenosine but not ATP receptors. The relative order of potency of adenosine analogues is consistent with activation of receptors of the A(1)-adenosine receptor subtype. These receptors appear to be prejunctional.

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Homo- and heteroexchange of adenine nucleotides and nucleosides in rat hippocampal slices by the nucleoside transport system.

Publications

Homo- and heteroexchange of adenine nucleotides and nucleosides in rat hippocampal slices by the nucleoside transport system.

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