The EFFECTS OF MONOVALENT AND DIVALENT CATIONS ON THE Α‐ADRENOCEPTOR OF INTACT HUMAN PLATELETS

Elliott, J.M.; Grahame‐Smith, D. G.

doi:10.1111/j.1476-5381.1982.tb09296.x

Cited by 9 publications

(3 citation statements)

References 12 publications

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“…We are therefore at present unable to explain this phenomenon. yohimbine is significantly reduced by the presence of either cation both in intact platelets and in membrane preparations (Elliott & Grahame-Smith, 1982b;Daiguchi et al, 1981) whereas the affinity of [ 3H] -dihydroergocryptine is unaffected (Elliott & Grahame-Smith, 1982b;Tsai & Lefkowitz, 1979). Divalent cations also reduce the affinity of [ 3H] -yohimbine binding in rat cerebral cortex membranes (Cheung, Barnett & Nahorski, 1982), suggesting a generalized difference in the regulation of the binding sites for r3H1 -dihydroergocryptine and r3H]-yohimbine o n a2-adrenoreceptors.…”

Section: Discussionmentioning

confidence: 99%

A COMPARISON OF α2‐ADRENORECEPTOR BINDING CHARACTERISTICS OF INTACT HUMAN PLATELETS IDENTIFIED BY [³H]‐YOHIMBINE AND [³H]‐DIHYDROERGOCRYPTINE

Boon

Elliott

Grahame‐Smith

et al. 1983

Journal of Autonomic Pharmacology

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The binding characteristics of [3H]-yohimbine on intact human platelets were investigated and compared to those of [3H]-dihydroergocryptine. A significant correlation (r = 0.92, P less than 0.01, n = 7) was observed between the inhibition of [3H]-yohimbine binding and of noradrenaline-induced platelet aggregation, indicating that [3H]-yohimbine binds to the alpha 2-adrenoreceptor responsible for noradrenaline-induced platelet aggregation. The binding capacity of [3H]-yohimbine in 20 young male volunteers was 39 +/- 2.2 fmol/10(8) platelets (mean +/- s.e.m.). This is considerably lower than the binding capacity of [3H]-dihydroergocryptine previously reported. Simultaneous analysis of [3H]-yohimbine and [3H]-dihydroergocryptine binding in 10 subjects showed a significantly lower binding capacity for [3H]-yohimbine (P less than 0.001, paired t-test). This difference was not present in every subject, and was consistent within individuals on repeated testing. Possible causes of this difference in radioligand binding are discussed.

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Section: Discussionmentioning

confidence: 99%

A COMPARISON OF α2‐ADRENORECEPTOR BINDING CHARACTERISTICS OF INTACT HUMAN PLATELETS IDENTIFIED BY [³H]‐YOHIMBINE AND [³H]‐DIHYDROERGOCRYPTINE

Boon

Elliott

Grahame‐Smith

et al. 1983

Journal of Autonomic Pharmacology

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“…In the platelet lysate preparation the affinity of agonists has been shown to be sensitive to the presence of specific cations and purine nucleotides Michel, Hoffman & Lefkowitz, 1980). Studies in our laboratory suggest that similar factors may account for the low affinity of agonists on intact platelets (Elliott & Grahame-Smith, 1981). …”

Section: Specificity Ofthe [3h]-dihydroergocryptine Binding Sitementioning

confidence: 99%

THE BINDING CHARACTERISTICS OF [³H]‐DIHYDROERGOCRYPTINE ON INTACT HUMAN PLATELETS

Elliott¹,

Grahame‐Smith²

1982

British J Pharmacology

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healthy, young, male subjects show a high degree of consistency both between subjects (Kd = 2.81 ± 0.27 nM; B,, = 63 ± 3 fmol/108 platelet: mean ± s.e.mean, n = 10) and between sampling occasions in a single subject (KSd= 3.28 nM± 13%; Bmax = 70 fmol/108 platelet ± 16%: mean ± coefficient of variation, n = 5). 6 There is no significant difference in the binding capacity of platelets from a group of elderly male subjects (mean age 73) compared to those from young males (mean age 27) or elderly females (mean age 77). The affinity of binding is slightly but significantly (P < 0.05) higher in the elderly male group compared to the two other groups.7 We conclude that [3H]-dihydroergocryptine binds to the a2-adrenoceptor of intact human platelets which is responsible for noradrenaline-induced platelet aggregation. The high consistency of the binding characteristics of [3H]-dihydroergocryptine indicate that this assay may be useful as a monitor of platelet o-adrenoceptor sensitivity in clinical investigation.

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“…It has been demonstrated that alpha2-adrenoceptors exist as a low affinity (a2L) state and a high affinity (a2H) state for agonists in broken cells, but the receptors in intact cells correspond to the a2L state (7). The present study was per formed to compare the affinities of DG-51 28 between the two affinity states of alpha2 adrenoceptors, in order to further clarify the binding properties of this antagonist.…”

mentioning

confidence: 99%

Selective Interaction of DG-5128 with a Low Agonist Affinity State of Alpha-2 Adrenoceptor

Yamanaka

Kigoshi

Muramatsu

1985

Japanese Journal of Pharmacology

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Abstract-Using rat cerebral cortex membranes, the inhibitory effect of DG-5128 against (3H)-clonidine binding was compared between low (a2L) (in the presence of EDTA) and high (a2H) affinity states (in the presence of excess magnesium) of alpha2-adrenoceptor for agonists. The K; value (pKi=6.79) of DG-5128 in the a2L state was 6.4 times higher than the value in the a2H state. Thus, DG-51 28 produces alpha2-adrenoceptor antagonism through the selective interaction with an a2L state of the receptor.

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The EFFECTS OF MONOVALENT AND DIVALENT CATIONS ON THE Α‐ADRENOCEPTOR OF INTACT HUMAN PLATELETS

Abstract: 1 We have examined the effects of monovalent and divalent cations and purine nucleotides on the binding of agonists and antagonists to the x-adrenoceptor of intact human platelets.

Cited by 9 publications

References 12 publications

A COMPARISON OF α2‐ADRENORECEPTOR BINDING CHARACTERISTICS OF INTACT HUMAN PLATELETS IDENTIFIED BY [³H]‐YOHIMBINE AND [³H]‐DIHYDROERGOCRYPTINE

A COMPARISON OF α2‐ADRENORECEPTOR BINDING CHARACTERISTICS OF INTACT HUMAN PLATELETS IDENTIFIED BY [³H]‐YOHIMBINE AND [³H]‐DIHYDROERGOCRYPTINE

THE BINDING CHARACTERISTICS OF [³H]‐DIHYDROERGOCRYPTINE ON INTACT HUMAN PLATELETS

Selective Interaction of DG-5128 with a Low Agonist Affinity State of Alpha-2 Adrenoceptor

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The EFFECTS OF MONOVALENT AND DIVALENT CATIONS ON THE Α‐ADRENOCEPTOR OF INTACT HUMAN PLATELETS

Abstract: 1 We have examined the effects of monovalent and divalent cations and purine nucleotides on the binding of agonists and antagonists to the x-adrenoceptor of intact human platelets.

Cited by 9 publications

References 12 publications

A COMPARISON OF α2‐ADRENORECEPTOR BINDING CHARACTERISTICS OF INTACT HUMAN PLATELETS IDENTIFIED BY [3H]‐YOHIMBINE AND [3H]‐DIHYDROERGOCRYPTINE

A COMPARISON OF α2‐ADRENORECEPTOR BINDING CHARACTERISTICS OF INTACT HUMAN PLATELETS IDENTIFIED BY [3H]‐YOHIMBINE AND [3H]‐DIHYDROERGOCRYPTINE

THE BINDING CHARACTERISTICS OF [3H]‐DIHYDROERGOCRYPTINE ON INTACT HUMAN PLATELETS

Selective Interaction of DG-5128 with a Low Agonist Affinity State of Alpha-2 Adrenoceptor

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A COMPARISON OF α2‐ADRENORECEPTOR BINDING CHARACTERISTICS OF INTACT HUMAN PLATELETS IDENTIFIED BY [³H]‐YOHIMBINE AND [³H]‐DIHYDROERGOCRYPTINE

A COMPARISON OF α2‐ADRENORECEPTOR BINDING CHARACTERISTICS OF INTACT HUMAN PLATELETS IDENTIFIED BY [³H]‐YOHIMBINE AND [³H]‐DIHYDROERGOCRYPTINE

THE BINDING CHARACTERISTICS OF [³H]‐DIHYDROERGOCRYPTINE ON INTACT HUMAN PLATELETS