Relation of Mammotropes to Mammary Tumors. V. Role of Mammotropes in Radiation Carcinogenesis.

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Abstract
This study was undertaken to demonstrate the role of mammotropic hormones in induction of mammary tumor by small doses of X-rays. X-rays (50r) and mammotropic hormones (administered in form of isologous functional mammotropic pituitary tumor grafts) alone produced no mammary tumors in female W/Fu rats within 7 months of treatment. In contrast, 53% rats treated with both developed mammary tumors. Administration of mammotropic hormones restored inhibition of mammary tumor development by ovariectomy. Most mammary tumors induced by radiation plus mammotropic hormones were adeno-carcinomas; a few were fibroadenomas. Three induced tumors tested failed to grow in males and grew in females uniformly only when stimulated with mammotropic hormones. Grafted fibroadenomas remained latent in many rats until administered mammotropic hormones brought about their rapid growth. Administration of this hormone could be delayed as long as 7 1/2 months. It is concluded that radiation bring about an irreversible modification of some cells, depending on severity of the dose; mammotropic hormones are not carcinogens but, as promoters of mammary epithelium, promote carcinogenesis and growth of some tumors.

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