The Effect of Oestrone on the Incidence of Mammary Carcinoma and Adenoma in C3Hf Breeders After Late Ovariectomy

THE effects on the incidence of spontaneous mammary carcinoma of breeding and of age in C3Hf mice have been recorded (Pullinger and Iversen, 1960). None of the tests done to detect the mammary tumour agent disclosed its presence in this strain (Pullinger, 1960a). A reduction in mammary tumour incidence in former breeding females after ovariectomy alone was reported (Pullinger, 1960b). In the present paper the incidence of mammary carcinoma and adenoma in C3Hf breeders after late ovariectomy with subsequent treatment with oestrone is described. MATERIALS AND METHODS Surplus breeders of generations F5 to F16 of the pure line C3Hf colony were ovariectomised at the age of 9 to 11 months. The operation and subsequent management were the same as that recorded for ovariectomy alone (Pullinger, 1960b) except that the animals were treated thereafter with oestrone once weekly for 30 weeks. One experimental group comprising 30 animals received 5,tg. weekly, the other of 23 received 10,ug. weekly. The oestrone was dissolved i