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