Metabolic utilization of linoleate and alpha-linolenate in cultured Sertoli cells.

1. The capacity of cultured Sertoli cells to synthesize long-chain polyunsatured fatty acids (PUFA) from the essential fatty acid (EFA) precursors 18:2 n-6 and 18:3 n-3 was tested, and the concentrations of each EFA required to obtain maximal incorporation into membrane lipids were determined. 2. The two EFA were added to the culture medium as free fatty acids complexed to albumin in a molar ratio of 12:1. 3. When the substrates were added individually, the maximal levels of biosynthesis were obtained with 0.7 micrograms/ml of 18:2 n-6 and 2 micrograms/ml of 18:3 n-3. 4. When the two EFA were added together, clear alterations in the behavior of the desaturases with regard to the n-6 and n-3 fatty acids were observed. 5. It was found that a concentration of 0.35 micrograms/ml of each EFA represented the "ideal" required level in order to ensure optimal incorporation of 22-carbon PUFA into the membrane lipids. 6. These results provide the first data on the definition of EFA requirements for Sertoli cells in culture.