Growth Inhibiting Agent in Extracts of Desiccated Mammary Gland

Abstract

Hormones, notably thyroxin, insulin, parathormone and epinephrine, have been shown to inhibit proliferation of the glandular tissues that produce them. 1 , 2 , 3 , 4 The availability of these hormones in concentrated form made possible a determination of their effect on the mitotic rate of the glands. The histological methods for calculating rates of proliferation in the endocrine organs are equally applicable to tissues that do not produce internal secretions. In this laboratory aqueous extracts of desiccated kidney were found to inhibit the proliferation of the epithelium of the renal tubules when injected intraperitoneally into young rats. 5 Saline extracts of desic- cated beef lactating mammary gland were made by the same method and injected into mice with spontaneous cancers of the mammary gland.∗ Tumor tissue was obtained by biopsy at the time of injection and the mitoses counted. Twenty-four hours later the animal was killed and the rate of proliferation determined. The results are shown in Table I. The experiments show that the extracts prepared from the mammary gland inhibit mitoses in the adenocarcinomata developing spontaneously in mice mammary glands. The mitoses in the tumors of control mice subjected to ether anesthesia and the same operative procedure were reduced not at all or to a much less degree. The inhibitory effect was seen about 24 hours after the injections and subsequently the tumors continued to grow at their usual rate.