The broad objective of this research is to delineate the basic reactions in the synthesis of lipids of specific structure (postional arrangement and composition of fatty acids) in mammalian tissues and to gain an insight into the role of essential fatty acids (EFA) in these reactions and in lipid transport or lipoprotein synthesis. It is also proposed to investigate the relationship of the synthesis of prostaglandins to the biological activity of EFA relative to metabolic functions of these acids and the development of caudal necrosis in hypophysectomized and EFA deficient rats. Interconversion and transformation (acyl exchange reactions) of fatty acids will be studied in vivo via intravenous and intratesticular injection of radioactive metabolities and in vitro in parallel tracer experiments with testicular tissues or subcellular fractions using normal and hypophysectomized rats. The effect of an EFA deficiency on the accumulation of fat in the liver of animals fed diets that influence lipogenesis will be investigated in order to define more clearly the role of these acids in lipid transport or lipoprotein synthesis. High resolution liquid chromatography will be used as a primary analytical technique through the development of a new hydrogen flame detector for lipids. This techniqe will be applied to the mass and radioactivity analyses of the lipid classes and prostaglandins especially in blood samples taken sequentially because of its speed and sensitivity.