In vivo interaction between steroidal alkylating agents and oestrogen receptors in rabbit uteri.

The binding of steroidal alkylating agents to specific tissue component is necessary for the selective distribution of these compounds to their target tissues. The in vivo interaction of Estracyt or NSC-112259 with oestrogen receptors may play an important role in their action mechanism. Both Estracyt and NSC-112259 which were administered in vivo, gradually reduced the binding of [3H] oestradiol to cytoplasmic oestrogen receptor in rabbit uteri. From this, it was suggested that a negligible amount of oestradiol was released from these compounds and that the oestradiol moiety was useful as a carrier for the nitrogen mustard moiety. And it appeared that the synthesis of a new receptor protein was inhibited by the nitrogen mustard moiety, thereby causing a decrease in the cytoplasmic oestrogen receptor level.