海水驯化对虹鳟鳃、肌肉和肝脏磷脂脂肪酸组成的影响

Differential Composition of Phospholipid Fatty Acids in Gill,Muscle and Liver of Rainbow Trout(Oncorhynchus mykiss)After Seawater Acclimation

海水养殖的虹鳟(Oncorhynchus mykiss)品质优于淡水养殖,但在海水驯化过程中会造成虹鳟死亡。为探究虹鳟在海水驯化过程的适应机制,本实验测定了海水驯化前后虹鳟鳃、肌肉和肝脏中磷脂脂肪酸的组成。研究显示,3种组织器官共检测出15~20种脂肪酸,其中饱和脂肪酸(Saturated fatty acids;SFA)中所占比例最高的是棕榈酸(Palmitic acid,16:0),单不饱和脂肪酸(Monounsaturated fatty acids;MUFA)中所占比例最高的是油酸(Oleic acid,18:1n9),多不饱和脂肪酸(Polyunsaturated fatty acids;PUFA)中所占比例最高的是DHA(Docosahexaenoic acid,22:6n3)。海水驯化可显著影响膜磷脂的不饱和指数(Unsaturated index;UI)、不饱和率(Unsaturated to saturated fatty acids ratio;U/S)、平均脂肪酸长度(Average number of C-atoms of the unsaturated fatty acid;LENGTH),且膜磷脂脂肪酸组成的变化存在显著的组织特异性。结果显示,海水驯化后,肌肉和鳃膜磷脂中SFA的比例显著上升,这使生物膜黏稠性(刚性)和抗氧化性提高,为了维持体内渗透压平衡,排泄多余离子,鳃中磷脂需要富集更多PUFA,尤其是与Na+/K+-ATP酶活性相关的花生四烯酸(20:4n6;ARA)和DHA(22:6n3)。与肌肉和鳃不同,肝脏膜磷脂中PUFA和MUFA均显著增加,使得膜流动性提高,代谢效率提高。

Rainbow trout(Oncorhynchus mykiss),an important salmonid fish,is widely cultivated around the world.Although the quality of rainbow trout cultured in seawater is better than in freshwater,seawater acclimation may cause death of the fish.In the present study,the fatty acid composition of phospholipids in muscle,gill and liver of rainbow trout were analyzed by gas chromatography after and before of seawater acclimation.There were 15~20 fatty acids detected in the three tissues’phospholipids of rainbow trout.The highest proportion in saturated fatty acids(SFA),monounsaturated fatty acids(MUFA),and polyunsaturated fatty acids(PUFA)is palmitic acid(16:0),oleic acid(18:1n9),and docosahexaenoic acid(DHA,22:6n3),respectively.The unsaturated index(UI),the unsaturated to saturated fatty acids ratio(U/S),and average number of C-atoms of the unsaturated fatty acid(LENGTH)of phospholipids in rainbow trout were significantly changed after seawater acclimation.Moreover,the modification of phospholipids is tissues-specific.After seawater acclimation,the fatty acid of muscle phospholipids of rainbow trout decreased in PUFA and increased in SFA,thus the biomembrane of muscle became more rigid.The level of DHA(22:6n3)and ARA(20:4n6),which is related to Na+/K+-ATPase enzyme activity,were significantly increased in gill phospholipids of seawater-acclimated trout.For liver phospholipids,the levels of PUFA and MUFA increased significantly after seawater acclimation,therefore the fluidity of biomembrane were enhanced.