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  • Title: [3H]-idazoxan binds with high affinity to two sites on hamster adipocytes: an alpha 2-adrenoceptor and a non-adrenoceptor site.
    Author: MacKinnon AC, Brown CM, Spedding M, Kilpatrick AT.
    Journal: Br J Pharmacol; 1989 Dec; 98(4):1143-50. PubMed ID: 2558757.
    Abstract:
    1. [3H]-idazoxan labels a single population of high affinity sites (Kd 2.26 +/- 0.02 nM; Bmax 372 +/- 25 fmol mg-1 protein) in hamster adipocyte membranes. In the presence of 1 microM yohimbine to preclude binding to alpha 2-adrenoceptors, the density of [3H]-idazoxan binding sites was reduced (287 +/- 18 fmol mg-1 protein) without an apparent decrease in the affinity (Kd 2.19 +/- 0.24 nM) of the radioligand. 2. Displacement studies indicate that alpha-adrenoceptor ligands with an imidazoline side chain completely inhibit [3H]-idazoxan binding to hamster adipocyte membranes; in contrast, the alpha 2-adrenoceptor antagonists yohimbine, rauwolscine, BDF 6143 and phentolamine inhibited only 20-30% of the specific binding with affinity values consistent with an interaction at alpha 2-adrenoceptors. 3. The low potency of noradrenaline and adrenaline in displacing [3H]-idazoxan binding to the second site on hamster adipocyte membranes indicates that it is unlikely that this site is a type of adrenoceptor. 4. These results suggest that [3H]-idazoxan binds with high affinity to two sites in hamster adipocytes: an alpha 2-adrenoceptor and a non-adrenoceptor imidazoline site.
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