EFFECTS OF SALINITY ON THE FATTY-ACID COMPOSITIONS OF TOTAL LIPID ANDINDIVIDUAL GLYCEROPHOSPHOLIPID CLASSES OF ATLANTIC SALMON (SALMO-SALAR) AND TURBOT (SCOPHTHALMUS-MAXIMUS) CELLS IN CULTURE

Cells from a relatively stenohaline marine species, turbot (Scophthalm us maximus) (TF) and an anadromous species, Atlantic salmon (AS) were cultured in media supplemented with NaCl to produce OPs varying from 3 00 to 500 mOsm kg(-1) and the direct effects of OP (salinity) on the f atty acid compositions of the main glycerophospholipid classes were de termined. The most dramatic effects of salinity on total lipid fatty a cids were observed in polyunsaturated fatty acids (PUFA) in TF cells. There was a graded decrease in the percentage of 18:2n-9, and conseque ntly total n-9 PUFA, and concomitantly increased percentages of both t otal n-3 and n-6 PUFA with increasing salinity. The increased n-3 and n-6 PUFA was due to significantly increased percentages of the major f atty acids in each of these groups, namely 22:6n-3 and 20:4n-6, respec tively. The reciprocal changes in n-9 PUFA and n-3/n-6 PUFA in TF cell total lipid resulted in the percentage of total PUFA not being signif icantly affected by changes in salinity. The graded decrease in 18:2n- 9 with increasing salinity in TF cells was observed in all the major g lycerophospholipids but especially PE, PI and PS. Increasing salinity resulted in graded increases in the percentages of 22:6n-3 in PE and P S in TF cells. The quantitatively greatest increase in the percentage of n-6 PUFA in TF cells occurred with 20:4n-6 in PC, PE and PL. There were less significant changes in the fatty acid compositions of glycer ophospholipids in AS cells. However, the proportion of total n-3 + n-6 PUFA in PE varied reciprocally with the proportion of dimethylacetals in response to salinity. Similar reciprocal changes between fatty aci ds in response to salinity were also evident in the quantitatively mor e minor glycerophospholipids PS and PI. In PS, the percentage of 22:6n -3 was significantly lower at 400 mOsm kg(-1) whereas the proportion o f total monoenes was significantly higher at that salinity. A similar inverse relationship between total monoenes and 20:4n-6 (and, to a les ser extent total saturates) in response to salinity was noted in PI. T he results show that environmental salinity, without whole-body physio logical stimuli, has direct effects on the fatty acid composition of m ajor glycerophospholipid classes in fish cells and that these effects differ in cells from different fish species.