Characteristics of the binding of [3H]-mepyramine to intact human U373 MG astrocytoma cells: evidence for histamine-induced H1-receptor internalisation

British Journal of Pharmacology
S Hishinuma, J M Young

Abstract

1. The kinetics of the binding of 5 nM [3H]-mepyramine to sites on intact human U373 MG astrocytoma cells, sensitive to inhibition by 2 microM pirdonium, were temperature-dependent. At 37 degrees C the half-time for association was 0.9 +/- 0.4 min and at 4 degrees C 19 +/- 3 min. Dissociation of bound [3H]-mepyramine was fast at 37 degrees C, t0.5 1.5 +/- 0.3 min, but at 6 degrees C dissociation initiated by dilution or addition of unlabelled mepyramine was negligible over 120 min. The very slow dissociation at 6 degrees C made it possible to reduce the level of pirdonium-insensitive binding from 56 +/- 5% to 39 +/- 5% by washing the cells in ice-cold medium before filtration. 2. The binding of [3H]-mepyramine sensitive to 2 microM temelastine, measured after 10 min equilibration at 37 degrees C, failed to saturate and was resolved into an hyperbola and an apparently linear component, whereas the fit to the binding of [3H]-mepyramine sensitive to 2 microM pirdonium was not significantly improved over that to an hyperbola. The mean Kd for the binding of [3H]-mepyramine to the saturable component, 2.5 +/- 0.4 nM, was in close agreement with the value of 3.5 nM for mepyramine derived from inhibition of histamine H1-receptor-mediat...Continue Reading

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Citations

Jan 31, 2014·Journal of Pharmacological Sciences·Yoshihiro UesawaMasaru Shoji
Oct 25, 2017·Journal of Neurochemistry·Shigeru HishinumaMasaru Shoji
May 8, 2009·American Journal of Physiology. Cell Physiology·Bernard FiorettiFabio Franciolini
Jan 1, 1997·British Journal of Pharmacology·J A KoenigP P Humphrey
Jul 6, 2005·Nihon yakurigaku zasshi. Folia pharmacologica Japonica·Shigeru Hishinuma, Masaki Saito

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