Evidence for an unidentified factor from the pituitary gland which affects the steroid metabolism in isolated hepatocytes and hepatoma cells of the rat

The effects of various extracts obtained from normal rat pituitary tissue (of female origin) and pituitary tumor tissue on the metabolism of 4-androstene-3,17-dione in isolated rat hepatocytes and cultured hepatoma (HTC) cells were investigated. Extracts that increased the 5α-reductase/16α-hydroxylase ratio in isolated hepatocytes also increased the 5α-reductase activity or the 5α-reductase/17-hydroxysteroid dehydrogenase ratio in HTC cells. These results indicate that both cell culture methods are suitable for use as in vitro assays for the pituitary principle which affects hepatic steroid metabolism in vivo. Using the above cell culture technique it has been possible to show that 'feminizing factor' activity is located in granules (densities 1.13 and 1.17g/cm³, respectively) in the female rat pituitary and in extracts from the cloned pituitary tumor (C₈11RAP). 'Feminizing factor' activity could not be duplicated by single standard anterior or posterior gland hormone preparations over a wide range of concentrations or combinations of such preparations. These results further strengthen the hypothesis put forward in earlier publications that an as yet unidentified pituitary principle may be involved in the control of hepatic steroid metabolism in the rat.