Metabolism of orally fed [3H]-eicosapentaenoic and [14C]-arachidonic acid in essential fatty acid-deficient rats.

Abstract

The metabolism of individual polyunsaturated fatty acids (PUFA) may be influenced differently by nutritional status and nutritional intake. In normal rats, radioactive arachidonic acid (20:4(n-6), is preferentially retained in tissue phospholipids compared to linoleic (18:2(n-6), or eicosapentaenoic acid (20:5(n-3). This study compares the fate of 20:4(n-6) and 20:5(n-3) acids in essential fatty acid-deficient (EFAD) rats. [3H]-20:5 and [14C]-20:4 were fed in a fish oil emulsion to EFAD rats. Tissue lipids were analysed for radioactivity at 1, 2 and 4 h. The conversion of [3H]-20:5 to docosapentaenoic acid (22:5) and docosahexaenoic acid (22:6) was examined using high performance liquid chromatography (HPLC). The recovery of 3H in small intestine was lower than that of 14C (26 vs. 36% after 4 h, p < 0.001), but was higher in the liver (26 of 3H vs. 22% of 14C, p < 0.01), kidneys (1.5 vs. 1.2%, p < 0.001) and colon (0.3 vs. 0.2%, p = 0.01). The percentages of 3H and 14C in phospholipids were investigated in intestine and liver, and were higher in EFAD rats than in normal rats, particularly for phosphatidylethanolamine (PE). The proportions of [3H]-20:5 transformed to 22:5 and 22:6 did not exceed 7% in the intestine and 10% in the liver. In conclusion, the metabolism of dietary fatty acids 20:4 and 20:5 differed less than in normal rats, mainly due to the preferential retention of both fatty acids in phospholipids.