本研究主要調查相同年齡不同魚體大小之海鱺其體脂肪蓄積及過氧化體增生活化受體 α mRNA（PPAR α mRNA）表現之差異。結果顯示，海鱺肝臟是主要脂肪的蓄積部位，在大型魚（體長約54.1公分；體重約1,287公克）肝臟脂肪含量可高達35%，遠大於小型魚（體長約36.8公分；體重約386公克）的26%（P < 0.05），脂肪又以中性脂質為主。大型魚血清中磷脂質、游離脂肪酸及總蛋白質含量明顯高於小型魚（P < 0.05）。大體型的海鱺，其肝臟脂肪細胞體積有較大的趨勢。在海鱺大型魚肝臟葡萄糖-6-磷酸脫氫.酵素活性明顯（P < 0.05）高於小型魚。脂肪酸合成.酵素活性隨蘋果酸.活性的增加而增加。小型魚肝臟PPAR α mRNA的表現量顯著高於大型魚，可能是由緊迫壓力所造成。

This study compared the differential lipid deposition, enzyme activities and mRNA expression of peroxisome proliferation-activated receptors (PPARs) in the liver of two sizes of cobias (Rachycentron canadum) that were of the same age. As the main site for lipid deposition, the liver contained 36% lipid in the large cobia (approximately 54 cm in total length and 1,300 g), which was significantly (P < 0.05) higher than that (26%) of the small cobia (37 cm and 390 g). Serum phospholipids, free fatty acids, total protein content and density of liver adipocytes were significantly higher in the large fish than smaller fish. While liver glucose-6-phosphate dehydrogenase activity was significantly higher in the large cobia than small fish, liver fatty acid synthetase activity was concurrent with liver malic enzyme activity. PPAR α mRNA expression in the liver was significantly higher in the small cobias than the large cobias.