title: Alpha-adrenoceptor changes after oestrogen treatment in platelets and other tissues in female rabbits.
abstract: alpha 2-Adrenoceptors on blood platelets have been widely used as a model for alpha-adrenoceptors in less accessible tissues. The effect of oestrogen (200 micrograms/day intramuscularly) on alpha 2-adrenoceptor number and function was studied in immature female rabbits. alpha 2-adrenoceptor number was measured in whole platelets, and membrane preparations of forebrain, hindbrain, spleen and kidney by radioligand binding. alpha 2-Adrenoceptor function was examined by measuring platelet aggregation in vitro and circulatory responses to selective alpha 2-adrenoceptor agonists in vivo. Oestrogen treatment resulted in a significant decrease in platelet alpha 2-adrenoceptor number and function. However, no changes were observed either in receptor number in other tissues or in responses to alpha 2-agonists in vivo. The results suggest that oestrogen modulation of rabbit platelet alpha 2-adrenoreceptor number and function may be different from that of brain, kidney and spleen. Caution should be exercised in extrapolating results from platelets to alpha-adrenoceptors at other sites.
mesh_terms: D000818:Animals; D001792:Blood Platelets / Q000032:analysis*; D001923:Brain Chemistry; D004967:Estrogens / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D007668:Kidney / Q000032:analysis; D010974:Platelet Aggregation / Q000187:drug effects; D011817:Rabbits; D011869:Radioligand Assay; D011942:Receptors, Adrenergic, alpha / Q000032:analysis / Q000187:drug effects*; D013154:Spleen / Q000032:analysis
chemical_list: D004967:Estrogens; D011942:Receptors, Adrenergic, alpha