Alpha-1 adrenoceptor subtypes (high, low) in human benign prostatic hypertrophy tissue according to the affinities for prazosin
✍ Scribed by Takeda, Masayuki; Hatano, Akihiko; Komeyama, Takeshi; Koizumi, Takako; Mizusawa, Takaki; Kanai, Toshio; Tomita, Yoshihiko; Maruyama, Kieko; Nagatomo, Takafumi
- Publisher
- John Wiley and Sons
- Year
- 1997
- Tongue
- English
- Weight
- 312 KB
- Volume
- 31
- Category
- Article
- ISSN
- 0270-4137
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✦ Synopsis
BACKGROUND.
A novel classification of ␣-1 adrenoceptor subtypes (High, Low) was applied to human benign prostatic hypertrophy (BPH) tissue. METHODS. Human BPH specimens were examined by a radioligand binding assay method using 3 H-prazosin, and those data were compared with preoperative therapies.
RESULTS.
(1) Scatchard analysis showed a high-affinity site (K d :27.18 ± 6.41 pM; B max : 9.29 ± 0.98 fM/mg protein; mean ± SE) as ␣ 1H , and a low-affinity site (K d : 4088.0 ± 744.34 pM, B max : 140.81 ± 19.98 fM/mg protein) as ␣ 1L subtype, for prazosin. (2) The K d and B max were not different in the nontreated group (n = 5), ␣ 1 blocker group (n = 5), and antiandrogen group (n = 5), in either ␣ 1 -high affinity or ␣ 1 -low affinity subtype. (3) Phenoxybenzamine had different pK i values for the above two adrenoceptor subtypes. Scatchard analysis showed that ␣ 1 -high affinity binding site disappeared in the presence of 1 M of phenoxybenzamine, and the K d and B max values in the presence of 1 M of phenoxybenzamine were almost identical to the ␣ 1 -low affinity site of the two subtypes. CONCLUSIONS. Human BPH tissue possesses both ␣ 1H -and ␣ 1L -adrenoceptor subtypes according to the affinities for prazosin, and only the ␣ 1H subtype can be completely inhibited by some concentration of phenoxybenzamine. Treatment by ␣ 1 blocker may not change the conditons of ␣ 1 -adrenoceptors in prostatic tissue.