Lipid composition of rat mammary carcinomas, mammary glands, and related tissues: endocrine influences.

The lipids of mammary glands and mammary carcinomas from rats in various hormonal states were studied and compared with each other, with adipose tissue, and with a new transplantable sarcoma derived from cultured mammary carcinoma cells. When large doses of estradiol-17 Beta were administered to the host, cells of a few carcinomas became engorged with triglyceride containing an increased proportion of C(10)-C(14) fatty acids-a characteristic of milk fat. Cancers capable of fatty transformation must retain in latent form the enzyme system for fatty acid synthesis possessed by mammary epithelium; estradiol-17 Beta apparently activates this system. The lipid composition of retroperitoneal adipose tissue resembled that of the mammary tissue of virgin rats; this indicates similarity between retroperitoneal fat and the adipose component of mammary gland. Relative to the dry nonfat material present, the phospholipid content of adipose tissue was greater than that of the other tissues. Generally, differences in lipid composition between tissues were in amounts of triglyceride present and proportions of fatty acids in the triglyceride fraction. The ratios of cholesterol and cholesterol ester to phospholipid were similar in normal and neoplastic tissues. The amounts of free fatty acid, monoglyceride, and diglyceride were roughly proportional to the amount of triglyceride present.