Arachidonic acid distribution in lipids of mammary glands and DMBA-induced tumors of rats.

In the phospholipid fractions, arachidonic acid represented a several fold higher percentage of fatty acids from DMBA-induced tumors and in mammary glands from midpregnant rats when compared to mammary glands from virgin rats. Arachidonic acid was not present in measurable quantities in the neutral lipid fractions of mammary glands from virgin rats. The arachidonic acid in the neutral lipid fraction of mammary glands from midpregnant rats was only detectable in the triglyceride-sterol ester fraction, but in that fraction less than 1% of the fatty acids were arachidonic acid. In the neutral lipids of the DMBA-induced tumors, it was of particular interest that a high proportion (19%) of the fatty acids in the diglyceride fraction consisted of arachidonic acid; no arachidonic acid was detected in the diglycerides of the normal tissues.