Involvement of adenosine deaminase and adenosine kinase in regulating extracellular adenosine concentration in rat hippocampal slices

doi:10.1016/0197-0186(94)00144-J

Neurochemistry International

Volume 26, Issue 4, April 1995, Pages 387-395

https://doi.org/10.1016/0197-0186(94)00144-J Get rights and content

Abstract

In this study the relative importance of adenosine deaminase and adenosine kinase in regulating extracellular adenosine concentration was investigated in rat hippocampal slices labelled with [³H]-adenine. The release of [³H]-purines evoked by electrical stimulation or energy depletion (oxygen and glucose deprivation) was measured and, using high-performance liquid chromatography (HPLC), the proportion of [³H]-label in the form of [³H]-adenosine, [³H]-inosine and [³H]-hypoxanthine was determined. In addition, endogenous purine release was measured by HPLC with UV detection. 10 μM 5-iodotubericidin (5-IT), an inhibitor of adenosine kinase, significantly increased endogenous adenosine release and altered the pattern of [³H]-purine release by increasing the proportion released as [³H]-adenosine, under basal conditions and after electrical stimulation or energy depletion. 5 μM erythro-9-(2-hydroxy-3-nonyl) adenosine (EHNA), an inhibitor of adenosine deaminase, also increased endogenous adenosine release and altered the pattern of [³H]-purine release evoked by energy depletion by decreasing the proportion of [³H]-label released as [³H]-hypoxanthine and [³H]-inosine, whilst approximately doubling that of [³H]-adenosine. In contrast, adenosine release was not altered by EHNA under basal conditions or electrical stimulation. It is concluded that under conditions which provide adequate oxygen and glucose, adenosine kinase plays a much greater role than adenosine deaminase in regulating the extracellular concentration of adenosine. However, adenosine deaminase becomes important in regulating extracellular adenosine concentration when adenosine formation is increased by energy depletion.

References (30)

L.P. Davies et al.
Halogenated pyrrolopyrimidine analogues of adenosine from marine organisms: pharmacological activities and potent inhibition of adenosine kinase
Biochem. Pharmac.
(1984)
L.P. Davies et al.
Studies on several pyrrolo-[2,3-d]pyrimidine analogues of adenosine which lack significant agonist activity at A1 and A2 receptors but have potent pharmacological activity in vivo
Biochem. Pharmac.
(1986)
T.V. Dunwiddie
The physiological role of adenosine in the central nervous system
Int. Rev. Biol.
(1985)
T.V. Dunwiddie
Purinergic transmission and its alternatives
Neurochem. Int.
(1990)
J.C. Fowler
Adenosine antagonists alter the synaptic response to in vitro ischaemia in the rat hippocampus
Brain Res.
(1990)
V.K. Gribkoff et al.
The adenosine antagonist 8-cyclopentyltheophylline reduces the depression of hippocampal neuronal responses during hypoxia
Brain Res.
(1990)
H.G.E. Lloyd et al.
Involvement of adenosine in synaptic depression induced by a brief period of hypoxia in isolated spinal cord of neonatal rat
Brain Res.
(1988)
H.G.E. Lloyd et al.
Intracellular formation and release of adenosine from rat hippocampal slices evoked by electrical stimulation or energy depletion
Neurochem. Int.
(1993)
P. Meghji et al.
Sites of adenosine formation, action and inactivation in the brain
Neurochem. Int.
(1990)
J.I. Nagy et al.
Adenosine deaminase and purinergic neuroregulation
Neurochem. Int.
(1990)

J.W. Phillis

Adenosine deaminase and the identification of purinergic neurons

Neurochem. Int.

(1990)

T. Zetterström et al.

Purine levels in the intact rat brain. Studies with an implanted perfused hollow fibre

Neurosci. Lett.

(1982)

J.R.S. Arch et al.

The control of the metabolism and the hormonal role of adenosine

Essays in Biochemistry

(1978)

M. Ballarin et al.

Extracellular levels of adenosine and its metabolites in the striatum of awake rats: inhibition of uptake and metabolism

Acta Physiol. Scand.

(1991)

F. Bontemps et al.

Mechanisms of elevation of adenosine levels in anoxic hepatocytes

Biochem. J.

(1993)

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^∗: Present address: Department of Pharmacology, The University of Sydney, NSW 2006, Australia.

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Involvement of adenosine deaminase and adenosine kinase in regulating extracellular adenosine concentration in rat hippocampal slices

Abstract

Biochem. Pharmac.

Biochem. Pharmac.

Int. Rev. Biol.

Neurochem. Int.

Brain Res.

Brain Res.

Brain Res.

Neurochem. Int.

Neurochem. Int.

Neurochem. Int.

Neurochem. Int.

Neurosci. Lett.

The control of the metabolism and the hormonal role of adenosine

Essays in Biochemistry

Extracellular levels of adenosine and its metabolites in the striatum of awake rats: inhibition of uptake and metabolism

Acta Physiol. Scand.

Mechanisms of elevation of adenosine levels in anoxic hepatocytes

Biochem. J.