THE INTRASPLENIC INJECTION OF SOME SYNTHETIC ESTROGENS AND PROESTROGENS

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Abstract
Diethylstilbestrol and hexestrol are inactivated in the liver, but to a lesser extent than estrone or a[alpha]-estradiol. The inactivation is related to the hydroxyl groups since esterification or methylation reduces the degree of inactivation. Ethinyl estradiol is the most active derivative of [alpha]-estradiol, but it is inactivated in the same proportion as is free estradiol. This suggests that the marked oral activity of ethinyl estradiol is due to its high potency rather than its resistance to hepatic inactivation. Triphenylethylene, triphenylchlor-ethylene and 9,10-di-n-propyl-9,10-dehydro-9,10-dihydroxy-1:2:5:6 dibenzanthracene are all potentiated in estrogenic activity by prior passage through the liver. It is suggested that passage through the liver is an important factor in the conversion of preestrogens to estrogens.