STUDIES ON THE CONVERSION OF OESTRADIOL LINKED TO A CYTOSTATIC AGENT (ESTRACYT®) IN VARIOUS RAT TISSUES

Abstract

Estracyt, a compound of N-mustard linked to estradiol phosphate, is used in the treatment of human prostatic cancer. The metabolism of this compound has been studied in different tissues of the rat both in vivo and in vitro. The phosphate group in position 17 of the estradiol moiety is rapidly split off from the compound. An estrone-cytostatic compound was extractable from the liver 1/2 h after Estracyt injection. The in vitro results showed that only the liver was able to convert the estradiol-cytostatic compound to an estrone-cytostatic one. When animals were killed 24 h after a 3-day period of Estracyt treatment, the dominating metabolite in the ventral prostate was an estrone-cytostatic compound, but traces of free estrone could also be demonstrated. No such compound was found in liver, diaphragm or blood at this time. In vivo an estrone-cytostatic compound seems to be preferentially retained in the ventral prostate after Estracyt injection while the metabolic conversion of the estradiol-cytostatic compound into an estrone-cytostatic one possibly occurs in the liver.