title: Altered steroid delta(4)-reductase activity in mammary tumor-bearing rats.
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.
mesh_terms: D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase / Q000378:metabolism*; D000818:Animals; D001646:Bile / Q000378:metabolism; D005260:Female; D008099:Liver / Q000201:enzymology*; D016031:Liver Transplantation; D008325:Mammary Neoplasms, Experimental / Q000201:enzymology* / Q000601:surgery; D009368:Neoplasm Transplantation; D010088:Oxidoreductases / Q000378:metabolism*; D051381:Rats; D013739:Testosterone / Q000494:pharmacology* / Q000652:urine
chemical_list: D013739:Testosterone; D010088:Oxidoreductases; D013741:3-Oxo-5-alpha-Steroid 4-Dehydrogenase