Identification of alpha 2-adrenoceptors and of non-adrenergic idazoxan binding sites in pancreatic islets from young and adult hamsters.
1. The current study was undertaken to investigate the characteristics of alpha 2-adrenoceptors and to search for the presence of NAIBS in hamster pancreatic islets. 2. Pancreatic islets were isolated from young (6-7 weeks) and adult (14-15 weeks) animals. 3. The identification of alpha 2-adrenoceptors using [3H]RX821002 indicated that adults exhibited higher number of alpha 2-adrenoceptors than the young animals (194 +/- 20 vs 105 +/- 16 fmol/mg protein) while the Kd value was unchanged. 4. Glucose-evoked insulin release was completely inhibited by the alpha 2-agonist clonidine (0.1 microM) whatever the age of the animals. Agonist inhibition curves showed the following rank order of potency: clonidine > UK14304 > adrenaline. 5. Blockade of UK14304-elicited inhibition by various antagonists indicated that yohimbine has a low affinity for the receptor supporting the conclusion that the receptor is of the alpha 2-D subtype. 6. Binding experiments with [3H]idazoxan under conditions allowing to discriminate between alpha 2-adrenoceptors and NAIBS showed that hamster pancreatic islets express a high number of NAIBS. The density of NAIBS was similar in young and adult hamsters (1550 +/- 245 and 1342 +/- 332 fmol/mg protein).
Lacombe
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INSERM U 317, Institut Louis Bugnard, CHU Rangueil, Toulouse, France.
Viallard
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Paris
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D000316:Adrenergic alpha-Agonists / Q000494:pharmacology; D000375:Aging / Q000378:metabolism*; D000818:Animals; D001665:Binding Sites; D006224:Cricetinae; D004146:Dioxanes / Q000378:metabolism*; D005947:Glucose / Q000378:metabolism; D019329:Idazoxan; D007328:Insulin / Q000378:metabolism; D007515:Islets of Langerhans / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008647:Mesocricetus; D011942:Receptors, Adrenergic, alpha / Q000378:metabolism*; D011955:Receptors, Drug / Q000378:metabolism*
D000316:Adrenergic alpha-Agonists; D004146:Dioxanes; D007328:Insulin; D011942:Receptors, Adrenergic, alpha; D011955:Receptors, Drug; C064580:idazoxan receptor; D005947:Glucose; D019329:Idazoxan