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Titolo:
CHARACTERISTICS OF THE BINDING OF [H-3] MEPYRAMINE TO INTACT HUMAN U373 MG ASTROCYTOMA-CELLS - EVIDENCE FOR HISTAMINE-INDUCED H-1-RECEPTOR INTERNALIZATION
Autore:
HISHINUMA S; YOUNG JM;
Indirizzi:
UNIV CAMBRIDGE,DEPT PHARMACOL,TENNIS COURT RD CAMBRIDGE CB2 1QJ ENGLAND UNIV CAMBRIDGE,DEPT PHARMACOL CAMBRIDGE CB2 1QJ ENGLAND
Titolo Testata:
British Journal of Pharmacology
fascicolo: 6, volume: 116, anno: 1995,
pagine: 2715 - 2723
SICI:
0007-1188(1995)116:6<2715:COTBO[>2.0.ZU;2-H
Fonte:
ISI
Lingua:
ENG
Soggetto:
SHORT-TERM DESENSITIZATION; MUSCARINIC CHOLINERGIC RECEPTORS; AGONIST-INDUCED DESENSITIZATION; BETA-ADRENERGIC RECEPTORS; PIG TAENIA CECUM; SMOOTH-MUSCLE; HELA-CELLS; TEMPERATURE-DEPENDENCE; PHOSPHOINOSITIDE HYDROLYSIS; LONGITUDINAL MUSCLE;
Keywords:
HISTAMINE H-1-RECEPTORS; DESENSITIZATION; RECEPTOR INTERNALIZATION; [H-3] MEPYRAMINE; U373 MG ASTROCYTOMA CELLS; PIRDONIUM;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Science Citation Index Expanded
Citazioni:
52
Recensione:
Indirizzi per estratti:
Citazione:
S. Hishinuma e J.M. Young, "CHARACTERISTICS OF THE BINDING OF [H-3] MEPYRAMINE TO INTACT HUMAN U373 MG ASTROCYTOMA-CELLS - EVIDENCE FOR HISTAMINE-INDUCED H-1-RECEPTOR INTERNALIZATION", British Journal of Pharmacology, 116(6), 1995, pp. 2715-2723

Abstract

1 The kinetics of the binding of 5nM [H-3]-mepyramine to sites on intact human U373 MG astrocytoma cells, sensitive to inhibition by 2 mu Mpirdonium, 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 [H-3]-mepyramine was fast at 37 degrees C, t(0.5) 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 veryslow dissociation at 6 degrees C made it possible to seduce the levelof pirdonium-insensitive binding from 56+/-5% to 39+/-5% by washing the cells in ice-cold medium before filtration. 2 The binding of [H-3]-mepyramine sensitive to 2 mu M temelastine, measured after 10 min equilibration at 37 degrees C, failed to saturate and was resolved into anhyperbola and an apparently linear component, whereas the fit to the binding of [H-3]-mepyramine sensitive to 2 mu M pirdonium was not significantly improved over that to an hyperbola. The mean K-d for the binding of [H-3]-mepyramine to the saturable component, 2.5+/-0.4 nM, wasin close agreement with the value of 3.5 nm for mepyramine derived from inhibition of histamine H-1-receptor-mediated inositol phosphate formation in U373 MG cells. 3 Curves for the inhibition of the binding of 5 nM [H-3]-mepyramine to U373 MG cells by histamine Hi-receptor antagonists were biphasic and were fitted to a two site-model. Affinities calculated from the best-fit IC50 values for the high-affinity site correlated well with those expected for binding to H-1-receptors. 4 The percentages of the high-affinity site in curves of the inhibition of [H-3]-mepyramine binding to intact U373 MG cells by two tertiary amine antagonists, norpirdonium and 4-methyldiphenhydramine, 68+/-3 and 63+/-4%, were significantly greater than the percentages of the high-affinity site in the inhibition curves of their quaternary derivatives, 50+/-1 and 45+/-3%, respectively. Similarly, the percentage of the high-affinity site for unlabelled mepyramine, 65+/-7%, was greater than for the non-cell penetrant H-1-antagonist temelastine, 42+/-5%. 5 Incubation of U373 MG cells with 100 mu M histamine at 37 degrees C, followed by washing twice in ice-cold medium and then incubation with 1-15 nM [H-3]-mepyramine for 120 min at 4 degrees C, resulted in a decrease in the binding of [H-3]-mepyramine sensitive to 2 mu M pirdonium, compared to control cells not exposed to histamine. The binding of [H-3]-mepyramine in the absence of pirdonium was not altered by histamine pretreatment, whereas the level of the pirdonium-insensitive binding was significantly increased, except after 1 min exposure to histamine. The decreases in the pirdonium-sensitive binding after 5, 10 and 60 min incubation with 100 mu M histamine were 41+/-6, 56+/-6 and 67+/-8%, respectively, but the decrease after 1 min incubation with histamine, 16 +/-8%, was not statistically significant. 6 The results are consistent with the binding of [H-3]-mepyramine to intact U373 MG cells being to both plasma membrane and intracellular histamine H-1-receptors. The high-affinity binding sensitive to the non-cell penetrant quaternary compounds and to temelastine is thus to plasma membrane H-1-receptors. On exposure to 100 mu M histamine receptors are translocated to the intracellular pool, since the change in the high-affinity binding of [H-3]-mepyramine is primarily in the level of the pirdonium-insensitive binding, rather than in the total binding.

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Documento generato il 06/04/20 alle ore 08:10:15