Prolonged exposure to inositol 1,4,5-trisphosphate does not cause intrinsic desensitization of the intracellular Ca super(2+)-mobilizing receptor

Here we have overloaded the intracellular Ca super(2+) stores of permeabilized rat hepatocytes by incubating them with ATP and super(45)Ca super(2+) in the presence of pyrophosphate, which precipitates Ca super(2+) within the lumen of the stores. Subsequent ATP removal initiated slow super(45)Ca sup...

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Bibliographic Details
Published in:The Journal of biological chemistry 1992-01, Vol.267 (23), p.16312-16316
Main Authors: Oldershaw, KA, Richardson, A, Taylor, C W
Format: Article
Language:English
Subjects:
calcium
effects on
exposure
hepatocytes
inositol 1,4,5-trisphosphate
receptors
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Summary:Here we have overloaded the intracellular Ca super(2+) stores of permeabilized rat hepatocytes by incubating them with ATP and super(45)Ca super(2+) in the presence of pyrophosphate, which precipitates Ca super(2+) within the lumen of the stores. Subsequent ATP removal initiated slow super(45)Ca super(2+) efflux that followed zero-order kinetics, allowing us to examine the effects of InsP sub(3) over a prolonged time course. InsP sub(3) produced a concentration-dependent increase in the super(45)Ca super(2+) efflux rate that was sustained for several min. The rate rapidly returned to the unstimulated level after the addition of decavanadate, a competitive antagonist of InsP sub(3) at its receptor. Prior incubation with a submaximal concentration of InsP sub(3) (1 mu M) did not affect the subsequent enhanced rate of super(45)Ca super(2+) efflux stimulated by a higher, but still submaximal, concentration of InsP sub(3) (3 mu M).
ISSN:0021-9258