The internal mammary artery (IMA) is currently the preferred conduit for myocardial revascularization. However, perioperative @entity2553 and a hypoperfusion state during maximal exercise may limit its use as a bypass graft. The mechanism of @entity2473 has not been clearly defined. Since beta-adrenoceptor activation plays a major role in vasorelaxation, the present study was carried out to investigate the beta-adrenoceptor responsiveness of @entity1 IMA smooth muscle. @entity3044 produced a concentration-dependent relaxation in endothelium-denuded IMA segments, precontracted with @entity2647 (maximal relaxation 46.33+/-5.45%). @entity2165 (10(-6)M) and @entity1169 (2x10(-7)M) inhibited @entity3044 -induced relaxation. While @entity2165 produced partial inhibition, @entity1169 caused a complete inhibition in a majority of the segments and a partial inhibition in a minority. @entity3047 , a selective @entity21276 agonist, produced a concentration-dependent relaxation in @entity2647 -precontracted rings of endothelium-denuded IMA (maximal relaxation 40.35+/-4.07%). @entity30828 , a beta-adrenoceptor partial agonist, produced a marked relaxation (58.65+/-6.2%) in endothelium-denuded IMA rings, precontracted with @entity2647 . @entity30828 -induced relaxation was resistant to blockade by @entity1169 (2x10(-7)M). Spontaneous contractions of IMA rings were also observed in some cases that were inhibited by @entity3044 and @entity3047 . This observation implies the important role of beta-adrenoceptor activation in prevention of @entity1 IMA @entity2473 . The results obtained in present study indicate that @entity1 IMA smooth muscle possesses an atypical beta-adrenoceptor together with beta1- and beta2-adrenoceptors. Regarding the relaxation induced in IMA rings by adding @entity3047 , the possible identical entities of IMA atypical beta-adrenoceptors and beta 3-adrenoceptors are suggested.

Coexistence of at least three distinct beta-adrenoceptors in XXXX internal mammary artery.

@entity1 :: ('9606', 'Species') :: ['human'] @entity1169 :: ('MESH:D011433', 'Chemical') :: ['propranolol'] @entity30828 :: ('MESH:C047975', 'Chemical') :: ['Cyanopindolol'] @entity3047 :: ('MESH:C057368', 'Chemical') :: ['BRL 37344'] @entity2647 :: ('MESH:D010656', 'Chemical') :: ['phenylephrine'] @entity2473 :: ('MESH:D013035', 'Disease') :: ['spasm'] @entity3044 :: ('MESH:D007545', 'Chemical') :: ['Isoproterenol', 'isoproterenol'] @entity2553 :: ('MESH:D020301', 'Disease') :: ['vasospasm'] @entity2165 :: ('MESH:D001262', 'Chemical') :: ['Atenolol', 'atenolol'] @entity21276 :: ('155', 'Gene') :: ['beta 3-adrenoceptor']
@entity1 :: (9606,Species) :: ['human']
