Unusual levels of phosphatidylcholine hydroperoxide in plasma, red blood cell, and livers of aromatic fish

Abstract

SUMMARY: Levels of phosphatidylcholine hydroperoxide (PC-OOH) in plasma, red blood cell (RBC), and livers of cultured and commercially available marine and freshwater fish were determined quantitatively by normal phase high-performance liquid chromatography (HPLC) equipped with a post-column detection system, using diphenyl-1-pyrenyl phosphine as a fluorescence reagent. The levels of plasma PC-OOH in non-aromatic fish, including yellowtail, amberjack, the Japanese flounder, sea bream, and rainbow trout ranged between 1.2 and 5.1 nmol/mL plasma. In contrast, the levels of PC-OOH in the plasma of aromatic fish, including the Japanese smelt, rainbow smelt, shishamo smelt, and sweet smelt were extremely high. The sweet smelt plasma contained the highest amount of hydroperoxide, amounting to 29.4 nmol/mL plasma. The levels of PC-OOH in non-aromatic fish RBC were low, ranging between 23.4 and 25.2 fmol/105 RBC. In contrast, a large amount of PC-OOH accumulated in all of the aromatic fish RBC used in the present study, ranging between 122 and 419 fmol/105 RBC. The PC-OOH levels in the sweet smelt and the Japanese smelt RBC were markedly high. The sweet smelt liver also contained a large amount of PC-OOH, amounting to 670 nmol/g tissue. This value was five times higher than those of some non-aromatic fish. Any marked difference in the contents of phospholipids and polyunsaturated fatty acids in the blood of sweet smelt and rainbow trout was not recognized. These results suggest that biogeneration of lipid hydroperoxide is an initial step in the development of certain volatile compounds in the aromatic fish.