The effect of culture on morphology, lipid and fatty acid composition, and polyunsaturated fatty acid metabolism of rainbow trout (Oncorhynchus mykiss) skin cells

摘要

Rainbow trout (Oncorhynchus mykiss) skin cell cultures were obtained bytrypsinisation of the tissue and grown in Leibovitz L-15 medium. Lipid classcompositions, and fatty acid profiles of total lipids and individualphospholipid classes were determined at different times of culture. Themetabolism of polyunsaturated fatty acids (PUFA) was investigated by incubatingprimary cultures after 7 and 14 days with [1-14C]18:2n-6 and [1-14C-]18:3n-3.The change in morphology between epithelial-like primary cultures andfibroblastic-like secondary subcultures was accompanied by alterations in thelipid composition. Polar lipids became predominant by 14 days in culture. Therelative proportions of phosphatidylcholine (PC), the most abundantphospholipid, phosphatidylinositol and cholesterol increased significantly,while sphingomyelin decreased. Saturated fatty acids, 18:1n-9, n-6 and n-9PUFAwere more abundant in total lipid in cultures at 14 days and 4 months than incells initially isolated which contained higher percentages of longer chainmonoenes and n-3PUFA. The changes in fatty acid composition with time in culturewere observed in all the major phospholipid classes. Rainbow trout skin cells inculture desaturated and elongated both 18:2n-6 and 18:3n-3, with 20:4n-6 and 20:5n-3 being the most abundant products, respectively. PC presented the highestincorporation of radioactivity, especially following incubation with 18:3n-3.Lipid metabolism in general increased with the age of primary cultures, withboth the amount of C18 PUFA incorporated and metabolised by desaturation/elongation significantly increased in 14 day cultures compared to 7 daycultures. Product/precursor ratios calculated for both n-6 and n-3 fatty acidsshowed that, while Δ6 desaturase activity was increased significantly with cellage, Δ5 desaturase activity was more affected by the fatty acid series, with 18:3n-3 being more readily transformed to 20:5n-3 than 18:2n-6 to 20:4n-6. Furtherdesaturation of 20:5n-3 to hexaenes was low. Overall, the data suggested thatthe trout skin cell cultures were more similar to mammalian skin fibroblaststhan mammalian epidermal/keratinocyte culture