MECHANISM OF INACTIVATION OFα-ESTRADIOL BY RAT LIVER “IN VITRO”1

Abstract
It is well known that the liver is the most important site of estrogen inactivation in different species. The early work of Zondek (1934) has shown that 95 per cent or more of the biological activity disappears when estrone is administered to man or rats or is incubated with rat liver “brei.” Heller (1940) studied the inactivation of estrone, estradiol and estriol by slices of various tissues and the influence of several inhibitors upon this phenomenon. Engel and Rosenberg (1945) have observed that aqueous liver extracts, obtained at different pH, inactivate estrone in prolonged incubation. More recently Levy (1947), working with a liver extract prepared by a modification of Zondek’s (1934) technique, has been able to study several properties of the inactivating system. The present study was undertaken for the purpose of securing additional information regarding the nature of the estrogen-inactivating mechanism.