Role of fatty acids of (n-3) and (n-6) series on alpha-linolenic acid desaturation and chain elongation in HTC cells.

The desaturation and chain elongation of [1-14C] alpha-linolenic acid were studied in HTC cells preincubated for 24 h in the presence of different unlabeled fatty acids of (n-3) and (n-6) series. After 24 h in the presence of [1-14C] alpha-18:3, cells transformed this acid into labeled 20:5 and 22:5(n-3) through the desaturation-elongation pathway and into 20:3 and 22:3(n-3) by the elongation reactions. The preincubation of HTC cells with (n-3) fatty acids (alpha-18:3, 20:5 and 22:6) produced an increase in the amount of [1-14C] alpha-18:3 that remained in the cells without being metabolized and consequently, a decrease in the last product formed, the 22:5(n-3) was observed. Simultaneously, the desaturation-elongation products decreased significantly and those of the elongation pathway were not modified, except when the cells were pre-incubated with the last fatty acid of this family (22:6) which increased this metabolic route. Fatty acids of (n-6) series (gamma-18:3, 20:3, 20:4 and 22:4) decreased the desaturation-elongation pathway and increased the elongation route from [1-14C] alpha-18:3. From these results, it can be concluded that fatty acids of (n-3) family and intermediates of (n-6) series would impair the [1-14C] alpha-18:3 metabolism at the delta 6 desaturation step. The fatty acid composition of the cells was also modified by the preincubation with (n-3) and (n-6) acids showing a decrease on delta 9 desaturation activity.