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Studies of Inositol Phosphate Export from Neuronal Tissue In Vitro
Author(s) -
Roberts Richard E.,
Marsden Charles A.,
Kendall David A.
Publication year - 1997
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1997.69031291.x
Subject(s) - inositol , carbachol , inositol phosphate , extracellular , endocrinology , medicine , muscarinic acetylcholine receptor , stimulation , intracellular , chemistry , basal (medicine) , biology , receptor , biochemistry , insulin
Recent in vivo microdialysis studies have demonstrated the presence of extracellular levels of inositol 1,4,5‐trisphosphate [Ins(1,4,5)P 3 ] that can be increased in a concentration‐dependent manner by muscarinic receptor activation. The aim of the present study was to determine whether extracellular levels of Ins(1,4,5)P 3 could be measured in vitro. Despite rapid increases in internal Ins(1,4,5)P 3 levels after stimulation with 1 m M carbachol, there was no change in external levels in both rat brain cortical slices and human neuroblastoma SH‐SY5Y cells. Suprafusion of myo ‐[ 3 H]inositol‐prelabelled hippocampal slices with 1 m M carbachol caused an increase in 3 H‐inositol phosphates over basal levels in the perfusate after 10 min, reaching a peak (223 ± 56% of basal) 20 min after suprafusion with carbachol was started. This response to carbachol was potentiated in the presence of 30 m M K + . Analysis of the individual 3 H‐inositol phosphates in the perfusate revealed that levels of [ 3 H]inositol monophosphate, [ 3 H]inositol bisphosphate, [ 3 H]inositol trisphosphate, and [ 3 H]inositol tetrakisphosphate were all significantly increased. A similar increase in extracellular 3 H‐inositol phosphates was demonstrated in SH‐SY5Y cells incubated with 1 m M carbachol for 30 min. This response was again enhanced by 30 m M K + , although the intracellular response was not potentiated. Possible roles for extracellular inositol phosphates are discussed.