The activities of steroid A4-5α-reductase and Δ4-5β-reductase were measured for 11 hepatomas of different growth rates and host livers. The A4-5α-reductase was determined in the microsomal fraction, and the Δ4-5β-reductase activity was measured in the 100, 000 x g supernatant fluid. Reduced Δ4-5α-and Δ4-5β-reductase activity was observed in the host liver of all animals bearing tumor in parallel with the increase in hepatoma growth rate. The decrease for both enzymes was quite similar and ranged from about 95% for the slow-growing hepatoma 44 to about 70% for the fast-growing hepatoma 42A. In the spectrum of hepatomas studied, the activities of both Δ4-5α-and Δ4-5β-reductase were significantly decreased in parallel with the increase in hepatoma growth rate. The decrease for A4-50-reductase ranged from 40% for the slow-growing hepatoma 44 to 8% for the fast-growing hepatoma 42A, while the decrease for A4-5a-reductase ranged from 3.8% for the slow-growing hepatoma 44 to 0.2% for the fast-growing hepatoma 42A. Stimulation of A4-5a-reductase activity with medroxyprogesterone acetate showed a 2-to 3-fold increase in enzyme activity in normal liver and host liver, but no effect was observed in hepatomas.
|Original language||English (US)|
|Number of pages||4|
|State||Published - May 1974|