Quantification and distribution of α1‐adrenoceptor subtype mRNAs in human proximal urethra

We performed RNase protection assays and in situ hybridization to investigate the ratio of the three α1-adrenoceptor subtype mRNAs, α1a, α1b and α1d, in human proximal urethra, and their localization in urethral cross-sections. As revealed by the RNase protection assays, α1a was the predominant subtype mRNA in both male and female urethral samples. α1d mRNA was detected only in the female sample, and α1b mRNA was not detected in any of the samples tested. The ratio of the abundance of the subtype mRNAs, α1a : α1b : α1d, was 100 : 0 : 0 in the male urethra and 90 : 0 : 10 in the female urethra. In situ hybridization studies showed no significant differences in the cross-sectional distribution of α1-adrenoceptor subtype mRNAs between male and female urethras. Intense α1a staining was observed in the smooth muscle of the urethra, but α1b and α1d staining was much less intense. Of the three cloned α1 subtypes, α1a is the most likely to be responsible for the contraction of the human urethra. Owing to the side effects of nonselective α1 drugs, α1-selective drugs may be clinically superior to nonselective drugs for the treatment of urethral disorders. British Journal of Pharmacology (1998) 123, 1289–1293; doi:10.1038/sj.bjp.0701731