Testosterone 5alpha-reductase in rat skin homogenates: measurement in the skin at various anatomical sites in males and females.

Experiments were disigned to find suitable conditions to determine the 5alpha-reducatase activity in rat skin homogenates. The dihydrotestosterone formation was linear until 15 min. The 5alpha- reductase was very heat labile at 37-c in absence of testosterone and NADPH since complete loss of activity occurred after one hour of preincubation. At OC, there was a 20% decrease after 5 hr. The enzyme activiity was measured in the skin at various anatomical sites. It was found to vary with each region in the following order in the male; tail,greater than scrotum greater than ear greater than genital skin greater than dorsum smaller than or equal to thorax greater than sole of the foot. In a few tissues, the enzyme activity was higher than in the prostate. Corresponding female tissues exhibited lower reductase activity except the sole of the foot in which the contrary was found. This significant sex difference indicates that sex hormones may be involved in the control of the levels of that enzyme in rat skin.