Lee, S.-H. Lee, D.-H. Lee, J.-A. Lee, W.-Y. Chung, B.-C. Choi, M.-H. 2024-01-20T15:30:46Z 2024-01-20T15:30:46Z 2021-08-31 2012-03 2233-4203 https://pubs.kist.re.kr/handle/201004/129517 5α-Dihydrotestosterone (DHT) is the primary active metabolite of testosterone, catalyzed by 5α-reductase (5αR) in the skin, prostate, and liver. In this study, the 5αR activity in rat liver S9 fraction in the presence of a NADPH-generating system was evaluated and compared by gas chromatography-mass spectrometry (GC-MS)-based in vitro assays. Testosterone and a 5αR inhibitor, finasteride, were added to the S9 fractions and incubated at 37oC for 1 h. Both testosterone and DHT were quantitatively measured and compared with two different GC-MS-based steroid profiling techniques. DHT was not detected by conventional GC-MS analysis in the absence of finasteride when the concentration of testosterone in the S9 fraction was less than 0.2 μM, whereas the isotope-dilution GC-MS (GC-IDMS) system was able to evaluate the 5αR activity. Because the S9 fraction contains more reactive enzymes and is easier to collect from tissues compared with a microsomal solution, the combination of the S9 fraction and GC-IDMS technique may be a promising assay for evaluating the 5αR activity in large-scale clinical studies. English Korean Society for Mass Spectrometry Comparative GC-MS based in vitro assays of 5α-reductase activity using rat liver S9 fraction Article 10.5478/MSL.2012.3.1.021 1 Mass Spectrometry Letters, v.3, no.1, pp.21 - 24 Mass Spectrometry Letters 3 1 21 24 scopus ART001912039 2-s2.0-84878762940 Article 5α-reductase Dihydrotestosterone GC-MS Isotope-dilution Liver microsome Testosterone