The influence of linoleic acid intake on the kinetics of adenine nucleotide translocase.

Dietary enrichment of mitochondrial polyenoic fatty acid content was associated with increased respiratory activity (Abuirmeileh and Elson). The influence of the membrane lipid composition on the adenine nucleotide translocase (AdNT) was studied in rats that were fed diets formulated with beef tallow (BT) to provide low or safflower oil (SO) to provide high contents of linoleic acid. The phosphatidylcholine/phosphatidylethanolamine ratio was 40% higher in the SO mitochondria due primarily to an increase in phosphatidylcholine. SO mitochondria exhibited 25% higher state 3 respiration, 50% higher state 4 respiration and 13% higher net ADP-dependent respiration than did the BT mitochondria. The relative RCR and ADP/O values of the SO mitochondria were slightly but significantly (p less than 0.01) lower. The kinetics of the AdNT were determined by the back exchange method (Pfaff and Klingenberg). At all assay temperatures, SO mitochondria exhibited a higher Km for ADP. However, addition of 5 mM carnitine to the assay mixture increased the affinity of the SO-AdNT giving Km values similar to that of the BT-AdNT. Washing the mitochondria with fat-free BSA had a similar, but lesser, effect. At 25 C and 37 C, the Vmax of the SO-AdNT were increased by 11-15% (p less than 0.05) which was independent of either BSA-wash or the presence of carnitine. According to Dixon plot studies, the SO-AdNT had a comparable Ki for atractylate but a slightly lower Ki for palmitoyl-CoA inhibition. The accumulation of acyl-CoA esters in the SO mitochondria was not ruled out. The overall results suggest that changes in mitochondrial membrane lipids accommodated an increased Vmax of the SO-AdNT, which in turn accounted for that part of the increased state 3 respiration dependent on ADP translocation.