RETROCONVERSION OF DHA IN LIVE FOOD

研究了活的食物，特别是卤虫无节幼体中二十二碳六烯酸（DHA）能否被逆转化为二十二碳五烯酸（DPA）或二十碳五烯酸（EPA）。在第一年，用直接法富集DHA。在卤虫培养液中添加EPA后，卤虫体内EPA含量增加，但DPA和DHA未检出。DHA强化卤虫体内DHA含量增加，DPA含量较少。此外，EPA含量比富含油酸（不含n-3脂肪酸）的卤虫增加得更多。另一方面，DHA富集的卤虫中的DHA含量累积不到EPA富集的卤虫中EPA含量的一半。这一结果表明，DHA可能在卤虫体内转化为DPA和EPA。为了证明从DHA到DPA的转化（这是逆转化的第一步），将[1-^<14>C] DHA直接富集到卤虫。结果表明，通过HPLC技术，在DPA组分中观察到轻微的放射性摄取。在第二年，还表明培养温度可能改变DHA的逆转化比例。在16 ℃和25 ℃的实验范围内以及在16 ℃保持6 h后改变到25 ℃的实验范围内，测定了卤虫对DHA的吸收。结果表明，在等温温度下，DHA的吸收没有明显的差异，但在随温度变化的范围内，放射性吸收增加了30%。这说明温度对卤虫体内脂肪酸的积累有影响。这表明，卤虫体内存在从DHA到EPA的逆转录途径，且卤虫以DHA为能量来源，因此DHA在卤虫体内难以积累。

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.