Selective blockade of alpha 1-adrenoceptors of porcine vascular smooth muscle cells by bunazosin.
The characteristics of bunazosin binding to alpha-adrenoceptors in the porcine aortic membranes were investigated using [3H]prazosin and [3H]yohimbine binding assays to identify alpha 1- and alpha 2-adrenoceptors, respectively. The extent of the inhibition (Ki values) of [3H]prazosin binding to alpha 1-adrenoceptors induced by bunazosin was 0.29 nmol/l and about the same as that induced by prazosin (Ki = 0.10 nmol/l). The Ki value of bunazosin inhibition of [3H]yohimbine binding to alpha 2-adrenoceptors was 350 nmol/l. There was over a 1000-fold difference in Ki value for bunazosin between alpha 1-and alpha 2-adrenoceptors. Thus, bunazosin is a highly alpha 1 selective agent in vascular smooth muscle.
Nishimura
J
J
Research Institute of Angiocardiology and Cardiovascular Clinic, Faculty of Medicine, Kyushu University, Fukuoka, Japan.
Kanaide
H
H
Miwa-Nishimura
N
N
Nakamura
M
M
D000317:Adrenergic alpha-Antagonists / Q000494:pharmacology*; D000818:Animals; D066298:In Vitro Techniques; D008566:Membranes / Q000187:drug effects / Q000378:metabolism; D008861:Microsomes / Q000378:metabolism; D009131:Muscle, Smooth, Vascular / Q000187:drug effects*; D009132:Muscles / Q000378:metabolism / Q000648:ultrastructure; D011224:Prazosin / Q000378:metabolism; D011799:Quinazolines / Q000494:pharmacology*; D013552:Swine; D015016:Yohimbine / Q000378:metabolism
D000317:Adrenergic alpha-Antagonists; D011799:Quinazolines; D015016:Yohimbine; C018176:bunazosin; D011224:Prazosin