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  • Title: Altered steroid delta(4)-reductase activity in mammary tumor-bearing rats.
    Author: Abul-Hajj YJ.
    Journal: Cancer Res; 1981 Apr; 41(4):1329-33. PubMed ID: 7011534.
    Abstract:
    The effect of mammary tumors on steroid delta(4)-reductase activity was investigated using in vitro and in vivo studies in three transplantable rat mammary tumors. Steroid delta(4)-5 alpha-reductase activity was measured spectrophotometrically and was significantly decreased in the host livers from R323OAC 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 5 beta-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 delta(4)-5 alpha-reductase enzyme which accounts for the observed increases in in vivo results. The surgical removal of the tumor abolishes the impairment in delta(4)-reductase activity.
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