[Utilization of linoleate and alpha-linolenate in peritubular cells and Sertoli cells in culture]

The capacity of cultured peritubular cells to synthesize long-chain polyunsaturated fatty acids (PUFA) from the essential fatty acid (EFA) precursors 18:2n-6 and 18:3n-3 was tested, and compared to the PUFA biosynthesis in Sertoli cells. The concentrations of each EFA required to obtain maximal incorporation into membrane lipids were determined. The two EFA were added to the culture medium as free fatty acids complexed to albumin in a molar ratio of 12:1. When the substrates were added individually, the maximal levels of biosynthesis in peritubular cells were obtained with 0.70 microgram/ml of 18:2n-6 or 18:3n-3 in culture medium. With Sertoli cells, the concentration of 0.70 micrograms/ml linoleate or of 2.00 micrograms/ml alpha-linolenate in culture medium appeared to correspond to levels required for maximal incorporation and utilization of the n-6 PUFA or n-3 PUFA. Incorporation and metabolic utilization were always more important in cultured Sertoli cells than in cultured peritubular cells. The peritubular cell appeared to incorporate linoleate les efficiently than alpha-linolenate at identical concentrations. In agreement with observations in other cell systems (15), we found a preferential utilization of 18:3n-3 over 18:2n-6 by the delta 6 desaturase in the peritubular cell and in the Sertoli cell.