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  • 1990-1994  (2)
  • 1
    ISSN: 1432-069X
    Keywords: Beta-adrenergic receptors ; Epidermis ; Keratinocytes ; Catecholamines ; Calcium ; Psoriasis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract Lesional psoriatic skin displays reduced responsiveness to Β-adrenergic stimulating agents. To elucidate whether the receptor protein itself is responsible for this, lesional and non-lesional psoritatic skin was investigated ex vivo for maximal Β-adrenergic binding density (B max) and Β-adrenergic binding affinity (K D). Epidermal crude membrane homogenates (ECMH) were prepared from split-thickness skin biopsies and saturated with the lipophilic Β-adrenergic antagonist (—)-125I-iodocyanopindolol (ICYP) as radioligand. Specific binding was saturable and Scatchard transformation of the binding data revealed a homogeneous class of Β-adrenergic receptors in all nine experiments. The maximal Β-adrenergic binding density was significantly less in lesional than in non-lesional psoriatic skin (B max=49.7 ± 7.2 fmol/mg protein vs. 67.1 ± 2.2 fmol/mg protein, n=9, P〈0.05). The binding affinity was similar in lesional and in non-lesional skin (K D=9.0 ± 1.5 pmol/l vs. 8.0 ± 0.9 pmol/l). These results could at least partially explain the reduced responsiveness of the Β-adrenergic system in lesional psoriatic skin seen after stimulation with Β-adrenergic agonists.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1432-069X
    Keywords: Beta-adrenoceptors ; HaCaT cell line ; Catecholamines ; Membrane receptor mechanisms ; Keratinocytes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Summary A non-tumorigenic keratinocyte cell line with complete epidermal differentiation capacity (HaCaT) was used in radioligand binding experiments to determine the number of beta-adrenoceptors. Intact cells were saturated with 3H-labelled (−)CGP-12177 (CGP), a hydrophilic non-selective beta-adrenergic antagonist as radioligand. In order to investigate the beta-adrenergic subtype selectivity, displacement experiments were performed with different antagonists and agonists. Binding of CGP to keratinocytes has been shown to be reversible and saturable and to have high affintiy (B max=114.0±8.8 fmol/107 cells with 6866 receptors/cell, K D=0.095±0.017 nmol/l; n=11). Betaadrenergic antagonists inhibited binding yielding monophasic displacement curves. IC50-values (nmol/l) were: propranolol (non-selective) 1.68; CGP-12177 (non-selective) 1.08; ICI 118,551 (beta2-selective) 2.92; bisoprolol (beta1-selective) 1230; and CGP-20712 (beta1-selective) 24980. Agonists displaced CGP in the order isoprenaline〉 adrenaline〉noradrenaline. We conclude that HaCaT cells express a high density of beta2-adrenoceptors providing a good model system to study adrenergic receptor mechanisms under reproducible experimental conditions in keratinocytes.
    Type of Medium: Electronic Resource
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