Quantal Ca2+ mobilization stimulated by inositol 1,4,5-trisphosphate in permeabilized hepatocytes

In several cell types, including hepatocytes, submaximal concentrations of Ins(1,4,5)P3 stimulate an initial rapid mobilization of intracellular Ca2+ stores that is followed by either no further Ca2+ release or very much slower release. Further additions of Ins(1,4,5)P3 then evoke further Ca2+ mobil...

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Bibliographic Details
Published in:Biochemical journal 1991-09, Vol.278 ( Pt 3) (3), p.705-708
Main Authors: Oldershaw, K A, Nunn, D L, Taylor, C W
Format: Article
Language:English
Subjects:
Animals
Calcium - metabolism
Calcium Radioisotopes
Cell Membrane Permeability
Inositol 1,4,5-Trisphosphate - pharmacology
Kinetics
Liver - drug effects
Liver - metabolism
Male
Rats
Rats, Inbred Strains
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Summary:In several cell types, including hepatocytes, submaximal concentrations of Ins(1,4,5)P3 stimulate an initial rapid mobilization of intracellular Ca2+ stores that is followed by either no further Ca2+ release or very much slower release. Further additions of Ins(1,4,5)P3 then evoke further Ca2+ mobilization. Such 'incremental' responses [Meyer & Stryer (1990) Proc. Natl. Acad. Sci. U.S.A. 87, 3841-3845] could result from all-or-nothing emptying of stores that differ in their sensitivities to Ins(1,4,5)P3 or from partial emptying of stores that are more uniformly sensitive, but unable to release all of their Ca2+ because the response to Ins(1,4,5)P3 rapidly attenuates. By measuring unidirectional 45Ca2+ efflux from intracellular stores stimulated with Ins(1,4,5)P3 under conditions where they continue to sequester 40Ca2+, we provide evidence suggesting that Ins(1,4,5)P3 stimulates all-or-nothing emptying of stores that differ in their sensitivities to Ins(1,4,5)P3, a quantal response pattern.
ISSN:0264-6021
1470-8728
DOI:10.1042/bj2780705