Functional identification of α1-adrenoceptor subtypes in human prostate: comparison with those in rat vas deferens and spleen
Journal
European Journal of Pharmacology
Journal Volume
265
Journal Issue
44198
Pages
61-66
Date Issued
1994
Author(s)
Abstract
The effects of some α1-adrenoceptor antagonists (prazosin, nonselective for the α1A- and α1B-adrenoceptor subtypes; 5-methyl-urapidil, selective for the α1A-adrenoceptor subtype, chloroethylclonidine, selective for the α1B-adrenoceptor subtype) and nifedipine were compared on contractile responses to noradrenaline or phenylephrine in human prostatic tissues, rat vas deferens and spleen. In rat vas deferens, nifedipine (1 μM), but not chloroethylclonidine (100 μM), almost completely abolished noradrenaline-induced contraction, the pA2 values for prazosin and 5-methyl-urapidil against noradrenaline being 9.29 and 8.55, respectively. In rat spleen, chloroethylclonidine reduced (by 57%) the maximum contraction induced by phenylephrine; nifedipine was ineffective. The log concentration-response curve was shifted significantly to the right; the pA2 values of prazosin and 5-methyl-urapidil against phenylephrine were 9.45 and 7.21, respectively. In human prostatic tissues, both nifedipine and chloroethylclonidine produced significant inhibition of noradrenaline-induced contractions. Chloroethylclonidine produced a 44% reduction of the maximum contraction to noradrenaline and shifted the log concentration-response curve to the right. In contrast, nifedipine, while reducing the maximum response to a similar extent, produced a small rightward shift in the log concentration-response curve. The pA2 values for prazosin and 5-methyl-urapidil against noradrenaline were 9.21 and 7.74, respectively. The pA2 values for prazosin in these three tissues did not vary significantly, whereas that for 5-methyl-urapidil in human prostatic tissue was intermediate between that in rat vas deferens and that in rat spleen: these tissues contain primarily α1A- and α1B-adrenoceptor subtypes, respectively. These results indicate that noradrenaline-induced contractions in human prostatic tissue are mediated by both α1A- and α1rmB-renoceptor subtypes. © 1994.
Type
journal article