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. 1987 Apr;90(4):763–769. doi: 10.1111/j.1476-5381.1987.tb11230.x

Bicarbonate-dependence of responses to ethylenediamine in the guinea-pig isolated ileum: involvement of ethylenediamine-monocarbamate.

D I Kerr, J Ong
PMCID: PMC1917213  PMID: 3580707

Abstract

gamma-Aminobutyric-acid (GABA)-mimetic responses were induced by ethylenediamine (EDA) in the isolated ileum of the guinea-pig maintained in bicarbonate buffered Krebs-Henseleit (KBC) solution, pH 7.4, 37 degrees C, the responses consisting of a contraction followed by a relaxation. There were no such responses to EDA in bicarbonate-free phosphate buffered (KPO) or HEPES buffered (KHO) Krebs solution, gassed with 100% O2, pH 7.4, 37 degrees C, yet the ileum responded to GABA in bicarbonate-free Krebs solution. Similar GABA-mimetic responses were induced by EDA in the isolated ileum maintained in bicarbonate-free KPO or KHO modified Krebs solution, gassed with O2, if HCO3- (5mM) was first added immediately before the test dose of EDA (0.1-1 mM), the threshold [HCO3-]being 2 mM for EDA-induced responses in these preparations. However, ileal GABA-mimetic responses were induced in bicarbonate-free KPO or KHO solutions by EDA that had been pretreated with carbon dioxide, where the final [HCO3-]in the bath did not exceed 25 microM. Ethylenediamine monocarbamate (synthetic EDAC) released [3H]-GABA from preloaded segments of ileum maintained in bicarbonate-free KPO or KHO solution containing amino-oxyacetic acid and beta-alanine, the release being sensitive to 3-mercaptopropionic acid which prevents GABA release. EDA itself did not evoke any such release in the absence of bicarbonate, but released [3H]-GABA from segments maintained in KBC solution.(ABSTRACT TRUNCATED AT 250 WORDS)

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Selected References

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