Regional distribution of 5α-reductase type 1 and type 2 mRNA along the human epididymis

Objective: To determine the regional distribution and relative expression of 5α-reductase type 1 and type 2 mRNA within the human testis and regions of the epididymis. Design: Prospective observational study. Setting: University academic medical center. Patient(s): Two young adult male organ donors. Intervention(s): None Main Outcome Measure(s): The distribution of 5α-reductase type 1 and type 2 mRNA in the testis and regions of the epididymis was detected by Northern blot analysis. The relative abundance of each 5α-reductase mRNA was evaluated using semiquantitative reverse transcriptase-polymerase chain reaction (RT-PCR) in which cyclophilin mRNA, a housekeeping gene product, was coamplified as the reference standard. Result(s): Northern blot analysis revealed the 5α-reductase type 2 transcript in the midcaput, distal caput, corpus, and proximal cauda of the epididymis, but the transcript was undetectable in the testis, proximal caput, and distal cauda region. No transcript for the type 1 isozyme was detected by Northern blot. The more sensitive RT-PCR showed low levels of type 1 mRNA in the testis and epididymis, with the highest abundance in the proximal caput. Type 2 mRNA of 5α-reductase was most abundant in the midcaput, was decreased in the more distal regions, and was more abundant than type 1 mRNA in all epididymal regions except for the proximal caput. Conclusion(s): Both 5α-reductase type 1 and type 2 mRNAs are present in the human epididymis. The type 2 isozyme mRNA is predominant, being more highly expressed than the low-abundance type 1 mRNA.