1 [3H]‐Clonidine binds to membranes prepared from guinea‐pig spleen with high affinity. 2 Kinetic experiments indicated that [3H]‐clonidine associates rapidly to the binding site and that the binding is reversible. A study of the dissociation of [3H]‐clonidine from splenic membranes revealed two components. The slowly dissociating component corresponded to a high affinity process (Kd= 2.1 nmol/1) in good agreement to that obtained by saturation analysis. 3 Over the concentration range used, saturation experiments revealed only a single population of sites with a dissociation constant (Kd) of 2.4 nmol/1 and a density of 5.1 pmol/g wet weight tissue. 4 Examination of the relative potency of a series of α‐adrenoceptor agonists and antagonists indicates that [3H]‐clonidine binding is to (α2‐adrenoceptors. 5 High levels of binding were obtained to lymphocytes prepared from guinea‐pig spleen and to membranes from the splenic capsule. Pretreatment of animals with 6‐hydroxydopamine produced changes in apparent affinity of binding with little change in the number of receptor sites. 6 It is concluded that [3H]‐clonidine labels a site resembling the a2‐adrenoceptor in guinea‐pig spleen. Few if any of these sites are located prejunctionally and a significant fraction are associated with lymphocytes.
|Number of pages||11|
|Journal||Clinical and Experimental Pharmacology and Physiology|
|Publication status||Published - 1 Jan 1982|
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