Do submaximal InsP3 concentrations only induce the partial discharge of permeabilized hepatocyte calcium pools because of the concomitant reduction of intraluminal Ca2+ concentration?
FEBS Lett
; 301(3): 287-90, 1992 Apr 27.
Article
em En
| MEDLINE
| ID: mdl-1577167
ABSTRACT
In several types of cells whose cytoplasmic Ca2+ is regulated by inositol phosphate derivatives, low concentrations of InsP3 added to permeabilized cell suspensions induce the rapid discharge of part of the InsPs-sensitive Ca2+ pool instead of slow monophasic release of Ca2+ from the entire pool. As a tentative explanation for this puzzling observation, sometimes called 'quantal release', it was suggested that the reduced intraluminal Ca2+ concentration remaining in the Ca2+ pool after a certain amount of Ca2+ had been released might allosterically reduce the channels' affinity for InsP3 and the corresponding InsP3-dependent Ca2+ efflux, and thus result in partial pool discharge (Irvine, R.F. (1990) FEBS Lett. 263, 5-9). We have tested this hypothesis by manipulating the Ca2+ pool contents with ionophore, and found that the rate of InsP3-dependent Ca2+ efflux after ionophore-induced partial discharge of the Ca2+ pools was much faster than what was predicted on the basis of this hypothesis. Heterogeneity of the Ca2+ pools appears to be a more likely reason for the 'quantal release' behavior.
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Bases de dados:
MEDLINE
Assunto principal:
Inositol 1,4,5-Trifosfato
/
Cálcio
/
Fígado
Tipo de estudo:
Prognostic_studies
Limite:
Animals
Idioma:
En
Revista:
FEBS Lett
Ano de publicação:
1992
Tipo de documento:
Article
País de afiliação:
França