Chloroethylclonidine Discriminates between α1A and α1B-Adrenoceptors in the Presence of Guanosine 5'-Triphosphate in Rabbit Thoracic Aorta

[摘要] References(21)Cited-By(4)Studies on the displacement of [3H]prazosin binding by the α1-agonist phenylephrine revealed the presence of at least high and low-affinity binding sites in membrane preparations prepared from rabbit thoracic aorta. Although the low-affinity site was reduced by the pretreatment of tissues with chloroethylclonidine, this site was unaffected by the same pretreatment of membrane preparations that did not contain the GTP analog. However, in membrane preparations with the metabolically stable GTP analog GTPγ-S (10-5M) and single cell preparations, the low-affinity site was completely eliminated by the chloroethylclonidine pretreatment. Displacement studies with the α1-antagonist WB4101 also revealed high- and low-affinity binding sites labeled by [3H]prazosin. Displacement curves of WB4101 obtained from membrane preparations in the presence of GTPγ-S (10-5M) did not differ from those in the absence of GTPγ-S. These results suggest that the low affinity phenylephrine binding site labeled by [3H]prazosin was selectively bound by the chloroethylclonidine used to pretreat the tissues, membrane preparation containing GTPr-S and single cells, and that chloroethylclonidine is able to recognize these two distinct subtypes of α1-adrenoceptors only when GTPγ-S is present.

[学科分类] 药理学

[关键词] GTPγ-S;Chloroethylclonidine;Thoracic aorta (rabbit)