Precise quantitation of 5alpha-reductase type 1 mRNA by RT-PCR in rat liver and its positive regulation by testosterone and dihydrotestosterone.

The liver is a multifunctional organ responsible for steroid hormones catabolism. Thus, the enzymes responsible for steroid catabolism are located in the liver, including the steroid 5alpha-Reductase (5alpha-R) (EC 1.3.99.5) which catalyzes the conversion of compounds with Delta(4,5) double bonds such as testosterone (T) into their respective reduced derivatives such as dihydrotestosterone (DHT), which are more hydrosoluble, therefore facilitating their excretion. We present precise measurements of mRNA levels of steroid 5alpha-Reductase type 1 isozyme (5alpha-R1) in the liver of male rats with different androgen status, using a quantitative RT-PCR coupled to laser-induced fluorescence capillary electrophoresis (LIF-CE). By means of this technique, we demonstrate a high level of expression of the gene that encodes 5alpha-R1 isozyme in male rat liver, and both T and DHT exert a positive control on the genetic expression of liver 5alpha-R1 isozyme. Since DHT does not contain a Delta(4,5) double bond, our results raise the possibility that hepatic 5alpha-R type 1 not only participates in the catabolism of steroids with Delta(4,5) double bonds, but also in other physiological functions, perhaps in the masculinization of the external genitalia in males with 5alpha-R type 2 gene deficiency.