CHARACTERIZATION AND LOCALIZATION OF ^|^alpha;1-ADRENOCEPTORS IN HUMAN PROSTATE

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Abstract
Radioligand binding assay and receptor autoradiography were undertaken to characterize alpha 1-adrenoceptors and to clarify their localization in human prostate. Eleven open prostatectomy specimens obtained from patients with benign prostatic hypertrophy were used for radioligand binding assay. The binding of [3H]-prazosin to prostatic crude membrane fraction was a saturable process of high affinity. Scatchard analysis of the specific [3H]-prazosin binding indicated the existence of a single population of receptor sites with an equilibrium dissociation constant of 1.00 +/- 0.19 nM (mean +/- SE) and a maximum binding capacity of 20.8 +/- 3.56 fmol/mg protein (mean +/- SE). alpha-Adrenergic antagonists competed for [3H]-prazosin binding in an order of potency: prazosin greater than or equal to bunazosin greater than phentolamine greater than yohimbine, suggesting that the binding sites for [3H]-prazosin have characteristics of alpha 1-adrenoceptors. To study the distribution of alpha 1-adrenoceptors in prostatic tissues obtained from total cystoprostatectomy specimens of six male bladder tumor patients, we used for autoradiography (+/-)-beta-[( 125I]Iodo-4-hydroxyphenyl)-ethyl-aminomethyl-tetralone [( 125I]-HEAT). Peripheral zone (PZ), central zone (CZ) and preprostatic region were dissected from the tissues and incubated with [125I]-HEAT, followed by an autoradiographic procedure. Distribution of alpha 1-adrenoceptors was quantitated by grain counting using a light microscope equipped with a micrometer. The specific binding sites for [125I]-HEAT were demonstrated predominantly in the fibromuscular stroma of CZ, that of PZ, preprostatic sphincter and subordinately in the glandular epithelium of CZ, but not in the glandular epithelium of PZ and periurethral glands.(ABSTRACT TRUNCATED AT 250 WORDS)

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