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 phos-pholipids 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 docosah-exaenoic acid (22:6) was examined using high performance liquid chromatogra-phy (HPLC). The recovery of ³H in small intestine was lower than that of ¹⁴C (26 vs. 36% after 4h, 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.

Key Words:

• arachidonic acid
• eicosapentaenoic acid
• essential fatty acid deficiency
• phospholipids
• phosphatidylcholine
• phosphatidylethanolamine