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COMPARATIVE STUDY ON α1 ‐ADRENOCEPTOR ANTAGONIST BINDING IN HUMAN PROSTATE AND AORTA
Author(s) -
Yamada Shizuo,
Suzuki Mayumi,
Tanaka Chiaki,
Mori Ryutaro,
Kimura Ryohei,
Inagaki Osamu,
Honda Kazuo,
Asano Masaharu,
Takenaka Toichi,
Kawabe Kazuki
Publication year - 1994
Publication title -
clinical and experimental pharmacology and physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.752
H-Index - 103
eISSN - 1440-1681
pISSN - 0305-1870
DOI - 10.1111/j.1440-1681.1994.tb02534.x
Subject(s) - prazosin , dissociation constant , antagonist , prostate , aorta , endocrinology , chemistry , medicine , urapidil , binding site , biology , receptor , biochemistry , blood pressure , heart rate , cancer
SUMMARY 1. Specific binding of [ 3 H]‐prazosin in prostatic and aortic membranes of humans was saturable and of high affinity (prostate: apparent dissociation constant, K d = 0.35 ± 0.03 nmol/L; aorta: K d = 0.26 ± 0.03 nmol/L). The density of [ 3 H]‐prazosin binding sites (B max ) for prostate and aorta was 546 ± 31 and 61.6 ± 1.6 fmol/mg protein, respectively. 2. Prazosin, YM617, naftopidil and urapidil competed with [ 3 H]‐prazosin for the binding sites in a dose‐dependent manner in the prostate and aorta of humans. The binding affinities of these antagonists in both tissues were compared, based on the inhibition constant, K i . Both prazosin and urapidil showed similar affinity to [ 3 H]‐prazosin binding sites in human tissue, whereas YM617 and naftopidil showed approximately a 12 and two times higher affinity, respectively, to α 1 ‐adrenoceptor sites of prostate than aorta. 3. The chloroethylclonidine treatment reduced partially the B max values for specific [ 3 H]‐prazosin binding in the prostate and aorta of humans with little effect on the K d values. 4. These data suggest that YM617 is a relatively selective antagonist of human prostatic α 1 ‐adrenoceptors.