[3H]Adenosine Transport in Synaptoneurosomes of Postmortem Human Brain

J. G. Gu, G. Kala, Jonathan Geiger

Research output: Contribution to journalArticle

12 Citations (Scopus)

Abstract

Abstract: Abstract: [3H]Adenosine transport was characterized in cerebral cortical synaptoneurosomes prepared from postmortem human brain using an inhibitor‐stop/centrifugation method. The adenosine transport inhibitors dipyridamole and dilazep completely and rapidly blocked transmembrane fluxes of [3H]adenosine. For 5‐s incubations, two kinetically distinguishable processes were identified, i.e., a high‐affinity adenosine transport system with Kt and Vmax values of 89 μM and 0.98 nmol/min/mg of protein, respectively, and a low‐affinity adenosine transport system that did not appear to be saturable. For incubations with 1 μM [3H]adenosine as substrate, intrasynaptoneurosomal concentrations of [3H]adenosine were 0.26 μM at 5 s and 1 μM at 600 s. Metabolism of accumulated [3H]adenosine to adenine nucleotides was 15% for 5‐s, 23% for 15‐s, 34% for 30‐s, 43% for 60‐s, and 80% for 600‐s incubations. The concentrations (μM) of total accumulated 3H‐purines ([3H]‐adenosine plus metabolites) at these times were 0.3, 0.5, 1.0, 1.3 and 5.6, respectively. These results indicate that in the presence of extensive metabolism, the intrasynaptoneurosomal accumulation of 3H‐purines was higher than the initial concentration of 1 μM [3H]adenosine in the reaction medium. For 5‐, 15‐, 30‐, 60‐, and 600‐s incubations in the presence of the adenosine deaminase inhibitor EHNA and the adenosine kinase inhibitor 5′‐iodotubercidin, metabolism of the transported [3H]adenosine was 14, 14, 16, 14, and 38%, respectively. During these times, total 3H‐purine accumulation was 0.3, 0.5, 0.5, 0.7, and 1.8 μM, respectively. Thus, the apparently “concentrative'’accumulation of 3H‐purines can be prevented by inhibition of adenosine metabolism and, taken together, these results suggest that adenosine transport in at least synaptoneurosomes prepared from postmortem human brain is via a nonconcentrative and equilibrative system.

Original languageEnglish (US)
Pages (from-to)2232-2237
Number of pages6
JournalJournal of Neurochemistry
Volume60
Issue number6
DOIs
StatePublished - Jan 1 1993

Fingerprint

Adenosine
Brain
Metabolism
Dilazep
Adenosine Deaminase Inhibitors
Adenosine Kinase
Enzyme inhibition
Dipyridamole
Adenine Nucleotides
Centrifugation
Metabolites
Fluxes

Keywords

  • 5′‐Iodotubercidin
  • Adenosine
  • Adenosine deaminase
  • Adenosine kinase
  • EHNA
  • Human brain.
  • Synaptoneurosome
  • Transport

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

Cite this

[3H]Adenosine Transport in Synaptoneurosomes of Postmortem Human Brain. / Gu, J. G.; Kala, G.; Geiger, Jonathan.

In: Journal of Neurochemistry, Vol. 60, No. 6, 01.01.1993, p. 2232-2237.

Research output: Contribution to journalArticle

@article{1e836aa197f5463694482074c1585e7f,
title = "[3H]Adenosine Transport in Synaptoneurosomes of Postmortem Human Brain",
abstract = "Abstract: Abstract: [3H]Adenosine transport was characterized in cerebral cortical synaptoneurosomes prepared from postmortem human brain using an inhibitor‐stop/centrifugation method. The adenosine transport inhibitors dipyridamole and dilazep completely and rapidly blocked transmembrane fluxes of [3H]adenosine. For 5‐s incubations, two kinetically distinguishable processes were identified, i.e., a high‐affinity adenosine transport system with Kt and Vmax values of 89 μM and 0.98 nmol/min/mg of protein, respectively, and a low‐affinity adenosine transport system that did not appear to be saturable. For incubations with 1 μM [3H]adenosine as substrate, intrasynaptoneurosomal concentrations of [3H]adenosine were 0.26 μM at 5 s and 1 μM at 600 s. Metabolism of accumulated [3H]adenosine to adenine nucleotides was 15{\%} for 5‐s, 23{\%} for 15‐s, 34{\%} for 30‐s, 43{\%} for 60‐s, and 80{\%} for 600‐s incubations. The concentrations (μM) of total accumulated 3H‐purines ([3H]‐adenosine plus metabolites) at these times were 0.3, 0.5, 1.0, 1.3 and 5.6, respectively. These results indicate that in the presence of extensive metabolism, the intrasynaptoneurosomal accumulation of 3H‐purines was higher than the initial concentration of 1 μM [3H]adenosine in the reaction medium. For 5‐, 15‐, 30‐, 60‐, and 600‐s incubations in the presence of the adenosine deaminase inhibitor EHNA and the adenosine kinase inhibitor 5′‐iodotubercidin, metabolism of the transported [3H]adenosine was 14, 14, 16, 14, and 38{\%}, respectively. During these times, total 3H‐purine accumulation was 0.3, 0.5, 0.5, 0.7, and 1.8 μM, respectively. Thus, the apparently “concentrative'’accumulation of 3H‐purines can be prevented by inhibition of adenosine metabolism and, taken together, these results suggest that adenosine transport in at least synaptoneurosomes prepared from postmortem human brain is via a nonconcentrative and equilibrative system.",
keywords = "5′‐Iodotubercidin, Adenosine, Adenosine deaminase, Adenosine kinase, EHNA, Human brain., Synaptoneurosome, Transport",
author = "Gu, {J. G.} and G. Kala and Jonathan Geiger",
year = "1993",
month = "1",
day = "1",
doi = "10.1111/j.1471-4159.1993.tb03509.x",
language = "English (US)",
volume = "60",
pages = "2232--2237",
journal = "Journal of Neurochemistry",
issn = "0022-3042",
publisher = "Wiley-Blackwell",
number = "6",

}

TY - JOUR

T1 - [3H]Adenosine Transport in Synaptoneurosomes of Postmortem Human Brain

AU - Gu, J. G.

AU - Kala, G.

AU - Geiger, Jonathan

PY - 1993/1/1

Y1 - 1993/1/1

N2 - Abstract: Abstract: [3H]Adenosine transport was characterized in cerebral cortical synaptoneurosomes prepared from postmortem human brain using an inhibitor‐stop/centrifugation method. The adenosine transport inhibitors dipyridamole and dilazep completely and rapidly blocked transmembrane fluxes of [3H]adenosine. For 5‐s incubations, two kinetically distinguishable processes were identified, i.e., a high‐affinity adenosine transport system with Kt and Vmax values of 89 μM and 0.98 nmol/min/mg of protein, respectively, and a low‐affinity adenosine transport system that did not appear to be saturable. For incubations with 1 μM [3H]adenosine as substrate, intrasynaptoneurosomal concentrations of [3H]adenosine were 0.26 μM at 5 s and 1 μM at 600 s. Metabolism of accumulated [3H]adenosine to adenine nucleotides was 15% for 5‐s, 23% for 15‐s, 34% for 30‐s, 43% for 60‐s, and 80% for 600‐s incubations. The concentrations (μM) of total accumulated 3H‐purines ([3H]‐adenosine plus metabolites) at these times were 0.3, 0.5, 1.0, 1.3 and 5.6, respectively. These results indicate that in the presence of extensive metabolism, the intrasynaptoneurosomal accumulation of 3H‐purines was higher than the initial concentration of 1 μM [3H]adenosine in the reaction medium. For 5‐, 15‐, 30‐, 60‐, and 600‐s incubations in the presence of the adenosine deaminase inhibitor EHNA and the adenosine kinase inhibitor 5′‐iodotubercidin, metabolism of the transported [3H]adenosine was 14, 14, 16, 14, and 38%, respectively. During these times, total 3H‐purine accumulation was 0.3, 0.5, 0.5, 0.7, and 1.8 μM, respectively. Thus, the apparently “concentrative'’accumulation of 3H‐purines can be prevented by inhibition of adenosine metabolism and, taken together, these results suggest that adenosine transport in at least synaptoneurosomes prepared from postmortem human brain is via a nonconcentrative and equilibrative system.

AB - Abstract: Abstract: [3H]Adenosine transport was characterized in cerebral cortical synaptoneurosomes prepared from postmortem human brain using an inhibitor‐stop/centrifugation method. The adenosine transport inhibitors dipyridamole and dilazep completely and rapidly blocked transmembrane fluxes of [3H]adenosine. For 5‐s incubations, two kinetically distinguishable processes were identified, i.e., a high‐affinity adenosine transport system with Kt and Vmax values of 89 μM and 0.98 nmol/min/mg of protein, respectively, and a low‐affinity adenosine transport system that did not appear to be saturable. For incubations with 1 μM [3H]adenosine as substrate, intrasynaptoneurosomal concentrations of [3H]adenosine were 0.26 μM at 5 s and 1 μM at 600 s. Metabolism of accumulated [3H]adenosine to adenine nucleotides was 15% for 5‐s, 23% for 15‐s, 34% for 30‐s, 43% for 60‐s, and 80% for 600‐s incubations. The concentrations (μM) of total accumulated 3H‐purines ([3H]‐adenosine plus metabolites) at these times were 0.3, 0.5, 1.0, 1.3 and 5.6, respectively. These results indicate that in the presence of extensive metabolism, the intrasynaptoneurosomal accumulation of 3H‐purines was higher than the initial concentration of 1 μM [3H]adenosine in the reaction medium. For 5‐, 15‐, 30‐, 60‐, and 600‐s incubations in the presence of the adenosine deaminase inhibitor EHNA and the adenosine kinase inhibitor 5′‐iodotubercidin, metabolism of the transported [3H]adenosine was 14, 14, 16, 14, and 38%, respectively. During these times, total 3H‐purine accumulation was 0.3, 0.5, 0.5, 0.7, and 1.8 μM, respectively. Thus, the apparently “concentrative'’accumulation of 3H‐purines can be prevented by inhibition of adenosine metabolism and, taken together, these results suggest that adenosine transport in at least synaptoneurosomes prepared from postmortem human brain is via a nonconcentrative and equilibrative system.

KW - 5′‐Iodotubercidin

KW - Adenosine

KW - Adenosine deaminase

KW - Adenosine kinase

KW - EHNA

KW - Human brain.

KW - Synaptoneurosome

KW - Transport

UR - http://www.scopus.com/inward/record.url?scp=0027336248&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=0027336248&partnerID=8YFLogxK

U2 - 10.1111/j.1471-4159.1993.tb03509.x

DO - 10.1111/j.1471-4159.1993.tb03509.x

M3 - Article

VL - 60

SP - 2232

EP - 2237

JO - Journal of Neurochemistry

JF - Journal of Neurochemistry

SN - 0022-3042

IS - 6

ER -