Abstract
We have stably expressed cDNA for the rat brain Ca2+ sensing receptor in Chinese hamster ovary cells. Stimulation of phosphatidylinositol hydrolysis and arachidonic acid (AA) release displayed markedly cooperative responses to Ca2+ with Hill coefficients of 4-5. Both phosphatidylinositol and AA responses were not detected below a threshold of 1.5 mM Ca2+. Mg2+ behaved as a partial agonist with only half the maximal inositol phosphate and AA responses displayed by Ca2+ and with a more shallow concentration-response slope. The potency of Mg2+ in augmenting inositol phosphate and AA responses, in the presence of 1.5 mM Ca2+, implies that serum Mg2+ concentrations attained in clinical conditions will influence the Ca2+-sensing receptor.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Arachidonic Acid / metabolism
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CHO Cells
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Calcium / metabolism*
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Calcium / pharmacology
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Cloning, Molecular
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Cricetinae
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DNA, Complementary / genetics
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Gene Expression
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Humans
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Hydrolysis
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Kinetics
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Magnesium / blood
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Magnesium / pharmacology
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Phosphatidylinositols / metabolism
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Rats
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Receptors, Calcium-Sensing
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Receptors, Cell Surface / drug effects
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Receptors, Cell Surface / genetics*
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Receptors, Cell Surface / metabolism*
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Second Messenger Systems
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Transfection
Substances
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DNA, Complementary
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Phosphatidylinositols
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Receptors, Calcium-Sensing
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Receptors, Cell Surface
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extracellular calcium cation-sensing receptor, rat
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Arachidonic Acid
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Magnesium
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Calcium