QUANTITATION OF ALPHA-1 AND BETA ADRENERGIC RECEPTOR DENSITIES IN THE HUMAN NORMAL AND HYPERTROPHIED PROSTATE

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  • ヒト前立腺組織中の交感神経受容体に関する研究

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Abstract

Using radioligand binding assays, both α1 and β adrenergic receptors of the human normal and hypertrophied prostatic tissue were quantitated, for the first time. For α1 adrenergic receptor assay, with 3H-prazosin as a ligand, the prostatic crude membrane fraction were incubated for 20min. at 30°C with or without 10μM phentolamine. The number of binding sites (NBS) and the dissociation constant (Kd) were calculated from the Scatchard analysis.<br>The number of binding sites of α1 adrenergic receptors in the normal prostatic tissue was determined 35.7±12.7fmol/mg protein (mean±S. D.), on the other hand, the NBS of it in the hypertrophied prostatic tissue was 50.3±14.6fmol/mg protein. In the hypertrophied prostate it was noticed that there was a significantly greater density of α1 adrenergic receptors than in normal prostate (p<0.05), although there was no difference in Kd between them.<br>It has recently been revealed that the human prostatic smooth muscle elicited supersensitive contractions to α1 adrenergic stimulants in benign prostatic hypertrophy, in vivo and in vitro. This supersensitive reaction seems to be due to the increase of α1 adrenergic receptors density in the hypertrophied prostatic tissue. Furthermore, it was speculated that the greater density of α1 adrenergic receptors in the hypertrophied prostate was caused by the denervation effect in the tissue.<br>For β adrenergic receptor assay, 3H-DHA (dihydroalprenolol) was used as a ligand. Although the incubation was performed for 30min. at 25°C, the method of binding assay was similar to the α1 adrenergic receptor assay. No difference in the NBS of β adrenergic receptors was revealed between normal and hypertrophied prostatic tissue. Lower affinity of β adrenergic receptors was obtained in the benign prostatic hypertrophy than normal prostate.

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