RETROCONVERSION OF DHA IN LIVE FOOD

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The study was investigated whether docosahexaenoic acid (DHA) can be retroconverted to docosapentaenoic acid (DPA) or eicosapentaenoic aicd (EPA) in live food, especially Artemia nauplii. In the first year, Artemia was enriched with DHA in dilrect method. When EPA was supplemented to Artemia medium, the content of EPA in Artemia increased, but DPA and DHA were not detected. In DHA-enriched Artemia, the DHA content was increased, and DPA was detected a little. Furthermore, the EPA content was increased more than that in Artemia enriched with oleic acid (containing no n-3 fatty acids). On the other hand, the DHA content in DHA-enriched Artemia accumulated less than half of the EPA content in EPA content in EPA-enriched Artemia. This result indicated that DHA might be converted to DPA and EPA in Artemia. In order to prove the conversion from DHA to DPA, which is the first step of retroconversion, [1-^<14>C] DHA was enriched directly to Artemia. The result showed that the radioactivity uptake was slightly observed in the DPA fraction by using HPLC technique. In the second year, it was also indicated that the cultural temperature may change the proportion of DHA retroconversion. DHA uptake in Artemia was examined in the experimental range maintained at 16 and 25ﾟC and the range maintained at 16ﾟC for 6h and changed to 25ﾟC As a result, a large difference in DHA uptake was not observed in the isothermal temperature, but in the range with the temperature change radioactive uptake was increased by 30%. This shows that temperature affect on the accumulation of fatty acids in Artemia. It is suggested that Artemia has retrocovert pathway from DHA to EPA, and Artemia use DHA as energy sources, so DHA is hard to accumulate in Artemia.