Feminization of hepatic S metabolism in male rats with a transplanted (MtT/F4).

After transplantation of MtT/F4 pituitary tumor cells to male rats of the Fisher strain, the masculine type of hepatic steroid metabolism was changed into a feminine pattern of enzyme activities. Liver metabolism of steroid hormones in female rats was relatively unaffected following transplantation of pituitary tumor cells. Futhermore, extract from MtT/F4 tumors and "autonomous" pituitary tissue increased the 5alpha-reductase activity of hepatoma cells in the culture (HTC cells) at subsaturation concentrations of the substrate 4-androstene-3, 17-dione by decreasing the apparent Km of the enzyme. It is concluded that the pituitary tumor (in accord with the secretion from an "autonomous" pituitary gland) secretes "feminotropin," a novel hypophyseal principle that probably is an important regulator of hepatic steriod metabolism. It is suggested that pituitary tumor tissue of the MtT/F4 type could be used as source of feminotropin in purification studies.