黄斑蓝子鱼LC-PUFA 合成代谢与渗透压调节的关系研究

为探讨黄斑蓝子鱼(Siganus canaliculatus)长链多不饱和脂肪酸(long-chain polyunsaturated fatty acids,LC-PUFA)合成代谢与渗透压调节的关系,本研究以鱼油(FO)和混合植物油(苏子油与双低菜籽油,VO)为脂肪源配制两种等氮等脂饲料,投喂饲养在3种盐度(10、20和32)下的黄斑蓝子鱼幼鱼8周后,分析了各处理组幼鱼的生长性能和鳃的磷脂脂肪酸组成、Na+/K+-ATPase(NKA)活力及其基因表达。结果显示,相同盐度下,VO组和FO组鱼的生长性能差异不显著(P0.05);FO组鱼鳃磷脂中的n-3 LC-PUFA含量显著高于VO组(P0.05),但VO组鱼的n-6 LC-PUFA水平显著高于FO组(P0.05);VO组鱼鳃的NKA酶活力及其m RNA表达量都显著高于FO组(P0.05)。不同盐度下,无论VO组还是FO组的鱼,盐度10组鱼的生长性能显著低于盐度20和32组(P0.05),而其鳃的LC-PUFA含量、NKA酶活力及其m RNA表达量都显著高于盐度20和32组(P0.05),各指标在后两个盐度组之间差异不显著(P0.05)。由此可见,盐度10对黄斑蓝子鱼具有一定的胁迫性,导致其生长性能较差。摄食鱼油脂肪源饲料,可以提高鱼鳃磷脂的n-3 LC-PUFA水平;而摄食植物脂肪源饲料时,鱼体可能通过自身合成的n-6LC-PUFA调控鳃的NKA基因表达及其酶活力以调节渗透压。

Research on relationship between LC-PUFA biosynthesis andosmoregulation in Siganus canaliculatus

To explore the relationship between osmoregulation and long-chain polyunsaturated fatty acid(LC-PUFA) biosynthesis in rabbitfish (Siganus canaliculatus), an 8-week feeding trial was performed in juvenilerabbitfish with diets that contained fish oil (FO) or a blend of vegetable oils (VO; perilla and canola oils) at threesalinities: 10, 20, and 32. The growth performance, fatty acid composition of gill phospholipids, and activity andexpression levels of gill Na+/K+ ATPase (NKA) under different treatments were analyzed. The results showed that,at the same salinity, there was no effect of dietary lipid source on growth performance (P>0.05), whereas n-3LC-PUFA content in gill phospholipids in the FO dietary groups was significantly higher than those in VO treatments(P<0.05). In particular, although the contents of n-6 LC-PUFA in VO-fed fish were lower than in FO-fedfish, the opposite was observed for n-6 LC-PUFA contents. Furthermore, the activity and mRNA expression levelsof gill NKA in VO groups were significantly higher than those in FO groups (P<0.05). Under different salinities,the growth indexes at a salinity of 10 were significantly lower than those at salinities of 20 and 32 in both dietarygroups (P<0.05), whereas the LC-PUFA contents, and activity and mRNA expression levels of NKA in fish fedVO were significantly higher than that in fish fed VO (P<0.05). In addition, there were no significant differencesin either of the higher two salinities treatments (P>0.05). The results indicate that a salinity of 10 may not suitablefor rabbitfish culture. Furthermore, FO-derived diets can improve n-3 LC-PUFA content in gill phospholipids,which helps maintain membrane lipid fluidity and osmotic balance. Alternatively, VO-derived diets can regulateosmotic pressure by synthesizing n-6 LC-PUFA to up-regulate NKA expression and activity.