Abstract
The effect of mammary tumors on steroid Δ4-reductase activity was investigated using in vitro and in vivo studies in three transplantable rat mammary tumors. Steroid Δ4-5α-reductase activity was measured spectrophotojnetrically and was significantly decreased in the host livers from R3230AC and MT/W9a-B but was increased in 7,12-dimethylbenz(a)anthracene-induced No. 14 tumor-bearing rats. There were no significant alterations of 5β-reductase activity in all animals investigated. In vivo studies using [14C]testosterone showed a similar pattern for saturation of the 4(5-double bond but that the more than doubled increase in 4,5-reduced metabolites observed in the in vivo studies in 7,12-dimethylbenz(a)anthracene-induced tumor-bearing rats cannot be explained by the increase observed in hepatic enzyme activity. Incubations with mammary tumor tissues showed that 7,12-dimethylbenz(a)anthracene-induced tumors have a very active Δ4-5α-reductase enzyme which accounts for the observed increases in in vivo results. The surgical removal of the tumor abolishes the impairment in Δ4-reductase activity.
Original language | English (US) |
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Pages (from-to) | 1329-1333 |
Number of pages | 5 |
Journal | Cancer Research |
Volume | 41 |
Issue number | 4 |
State | Published - Apr 1 1981 |