We previously found that linoleate, arachidonate and alpha-linoleate are effective (a) in lowering activities of liver lipogenic enzymes of EFA-deficient rats or fasted rats refed a fat-free diet and (b) in restoring volume oscillations of liver mitochondria when fed to EFA-deficient rats. Docosahexaenoate (22:6n3, from alpha-linolenate) is effective in reducing lipogenic enzyme activities but does not restore mitochondrial volume oscillations. We also found that liver cAMP-phosphodiesterase activity is elevated in EFA-deficient rats, an explanation for lower liver cAMP response after glucagon injection in EFA-deficient rats. We plan to investigate how different unsaturated fatty acids affect short-term control of fatty acid synthesis in intact rats and isolated tissue preparations. We plan to test whether polyunsaturated fatty acids can lower activities of lipogenic enzymes in other conditions which elevate activities of these enzymes. We plan to measure soluble and particulate cyclic nucleotide phosphodiesterase activity in EFA-deficient rats and to determine how these activities change in response to feeding essential fatty acids. Physical properties of lecithins containing different C18 and C20-unsaturated fatty acids will be compared, to determine how differences in the location and number of double bonds may affect lecithin properties. BIBLIOGRAPHIC REFERENCES: Louis, S.L., Brivio-Haugland, R.P. and Williams, M.A. Effect of essential fatty acid deficiency on activity of liver plasma membrane enzymes in the rat. J. Supramolecular Structure 4, 487-496, 1976. Brivio-Haugland, R.P., Louis, S.L. Musch, K., Waldeck, N. and Williams, M.A. Liver plasma membranes from essential fatty acid-deficient rats. Isolation, fatty acid composition and activities of 5'-nucleotidase, ATPase and adenylate cyclase. Biochim, Biophys. Acta 433, 150-163, 1976.