Quantification and distribution of α 1 ‐adrenoceptor subtype mRNAs in human vas deferens: comparison with those of epididymal and pelvic portions

1 This study was intended to quantify the amounts of the α 1 ‐adrenoceptor subtype mRNAs in human vas deferens, and demonstrate the receptor subtype responsible for the vas contraction. 2 The RNase protection assay showed that the mean total amount of α 1a mRNA was 7.4±2.2 pg/5 μg of poly (A) + RNA (97.0% of the total α 1 mRNA) in the epididymal portion (E‐vas) and 4.9±0.8 pg/5 μg of poly (A) + RNA (96.3% of the total) in the pelvic portion (P‐vas). The E‐vas showed a tendency to have a greater α 1a mRNA abundance than the P‐vas ( P =0.11). The α 1b and α 1d mRNAs were absent or of extremely low abundance. 3 By an in situ hybridization, the α 1a and α 1d mRNAs were recognized in the smooth muscle cells of the E‐vas and the P‐vas, and the distribution pattern the same in both tissues. The α 1b mRNA positive site was scarcely detectable in both vas portions. 4 In a functional study, l ‐phenylephrine produced concentration‐dependent contraction in the E‐vas (E max =2.24±0.70 g; pD 2 =5.32±0.09) and the P‐vas (E max =2.46±0.46 g; pD 2 =5.07±0.12). KMD‐3213, a novel α 1A ‐adrenoceptor‐selective antagonist, caused parallel rightward shifts of the concentration–response curves for l ‐phenylephrine. Apparent pK B values were 9.90±0.16 for the E‐vas and 9.71±0.17 for the P‐vas. There was no significant difference in E max , pD 2 or pK B estimates between the two portions. 5 We have found that α 1a mRNA is predominant in the human vas deferens, and confirmed that contraction of this organ is mediated by the α 1A ‐adrenoceptor.British Journal of Pharmacology (1997) 122 , 1009–1014; doi: 10.1038/sj.bjp.0701485