Interactions of divalent cations and guanine nucleotides at α2-noradrenergic receptor binding sites in bovine brain mechanisms

D. C. U'Prichard, Solomon H Snyder

Research output: Contribution to journalArticle

Abstract

Guanine nucleotides selectively decrease binding of the agonist ligands [3H]clonidine and [3H]epinephrine to α2-noradrenergic receptors in calf cortex membranes. In the presence of 1.0 mM-calcium, -magnesium, or -manganese, inhibition by GTP of [3H]clonidine binding is reversed, so that low concentrations of GTP increase [3H]clonidine binding, whereas high GTP concentrations cause a secondary decrease. In the presence of divalent cations, low concentrations of guanyl-5'-yl imidodiphosphate [Gpp(NH)p], unlike GTP, do not increase binding. Differences between effects of GTP and Gpp(NH)p in the presence of divalent cations are also observed with [3H]epinephrine binding to rat and calf cortex α2-receptors. In reversing the inhibition of α2-agonist binding by GTP, manganese, with an ED50 of 21 μM, is much more potent and effective than magnesium or calcium. Manganese by itself increases [3H]clonidine binding by 20%, an effect which is irreversible, while the interactive effects of manganese and GTP are reversible. Divalent cations also antagonize the sodium-induced inhibition of α2-agonist binding in calf cortex membranes, and manganese has similar ED50 values in antagonizing both sodium and GTP.

Original languageEnglish (US)
Pages (from-to)385-394
Number of pages10
JournalJournal of Neurochemistry
Volume34
Issue number2
StatePublished - 1980

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Guanine Nucleotides
Divalent Cations
Guanosine Triphosphate
Clonidine
Brain
Guanylyl Imidodiphosphate
Binding Sites
Manganese
Magnesium
Epinephrine
Sodium
Calcium
Membranes
Rats
Ligands
manganese GTP

ASJC Scopus subject areas

  • Biochemistry
  • Cellular and Molecular Neuroscience

Cite this

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abstract = "Guanine nucleotides selectively decrease binding of the agonist ligands [3H]clonidine and [3H]epinephrine to α2-noradrenergic receptors in calf cortex membranes. In the presence of 1.0 mM-calcium, -magnesium, or -manganese, inhibition by GTP of [3H]clonidine binding is reversed, so that low concentrations of GTP increase [3H]clonidine binding, whereas high GTP concentrations cause a secondary decrease. In the presence of divalent cations, low concentrations of guanyl-5'-yl imidodiphosphate [Gpp(NH)p], unlike GTP, do not increase binding. Differences between effects of GTP and Gpp(NH)p in the presence of divalent cations are also observed with [3H]epinephrine binding to rat and calf cortex α2-receptors. In reversing the inhibition of α2-agonist binding by GTP, manganese, with an ED50 of 21 μM, is much more potent and effective than magnesium or calcium. Manganese by itself increases [3H]clonidine binding by 20{\%}, an effect which is irreversible, while the interactive effects of manganese and GTP are reversible. Divalent cations also antagonize the sodium-induced inhibition of α2-agonist binding in calf cortex membranes, and manganese has similar ED50 values in antagonizing both sodium and GTP.",
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N2 - Guanine nucleotides selectively decrease binding of the agonist ligands [3H]clonidine and [3H]epinephrine to α2-noradrenergic receptors in calf cortex membranes. In the presence of 1.0 mM-calcium, -magnesium, or -manganese, inhibition by GTP of [3H]clonidine binding is reversed, so that low concentrations of GTP increase [3H]clonidine binding, whereas high GTP concentrations cause a secondary decrease. In the presence of divalent cations, low concentrations of guanyl-5'-yl imidodiphosphate [Gpp(NH)p], unlike GTP, do not increase binding. Differences between effects of GTP and Gpp(NH)p in the presence of divalent cations are also observed with [3H]epinephrine binding to rat and calf cortex α2-receptors. In reversing the inhibition of α2-agonist binding by GTP, manganese, with an ED50 of 21 μM, is much more potent and effective than magnesium or calcium. Manganese by itself increases [3H]clonidine binding by 20%, an effect which is irreversible, while the interactive effects of manganese and GTP are reversible. Divalent cations also antagonize the sodium-induced inhibition of α2-agonist binding in calf cortex membranes, and manganese has similar ED50 values in antagonizing both sodium and GTP.

AB - Guanine nucleotides selectively decrease binding of the agonist ligands [3H]clonidine and [3H]epinephrine to α2-noradrenergic receptors in calf cortex membranes. In the presence of 1.0 mM-calcium, -magnesium, or -manganese, inhibition by GTP of [3H]clonidine binding is reversed, so that low concentrations of GTP increase [3H]clonidine binding, whereas high GTP concentrations cause a secondary decrease. In the presence of divalent cations, low concentrations of guanyl-5'-yl imidodiphosphate [Gpp(NH)p], unlike GTP, do not increase binding. Differences between effects of GTP and Gpp(NH)p in the presence of divalent cations are also observed with [3H]epinephrine binding to rat and calf cortex α2-receptors. In reversing the inhibition of α2-agonist binding by GTP, manganese, with an ED50 of 21 μM, is much more potent and effective than magnesium or calcium. Manganese by itself increases [3H]clonidine binding by 20%, an effect which is irreversible, while the interactive effects of manganese and GTP are reversible. Divalent cations also antagonize the sodium-induced inhibition of α2-agonist binding in calf cortex membranes, and manganese has similar ED50 values in antagonizing both sodium and GTP.

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