Original article

N–3 fatty acid deficiency in the rat pineal gland: effects on phospholipid molecular species composition and endogenous levels of melatonin and lipoxygenase products

Correspondence to: Hee-Yong Kim.

N–3 essential fatty acid deficiency affects a number of biological and physiological processes. In this study, we investigated the effect of n–3 essential fatty acid status on two key pineal biochemical functions, melatonin production and lipoxygenation, using pineal glands from rats given an n–3-adequate or n–3-deficient diet. The pineal total lipid profile and phospholipid molecular species distribution altered by n–3 deficiency were evaluated in parallel. In pineal glands from n–3-deficient rats, an 87% reduction of 22:6n–3 (docosahexaenoic acid) was observed, and this decrease was accompanied by increases in 22:4n–6 (docosatetraenoic acid, 3-fold), 22:5n–6 (docosapentaenoic acid, 12-fold), and 20:4n–6 (arachidonic acid, 48%). The significant decrease of 22:6n–3 containing species in phosphatidylcholine (PC), phosphatidylethanolamine (PE), and phosphatidylserine (PS) was also evident. These decreases in 22:6n–3 containing PL species were compensated by substantial accumulations of 22:4n–6 or 22:5n–6 and slight increases in 20:4n–6 containing PL species in PC and PE. In PS, however, the accumulation of n-6 species was not adequate to compensate for the loss of 22:6n–3 species. N–3 deficiency significantly reduced non-esterified 20:4n–6 and 22:6n–3 levels in pineals (25% and 65%, respectively). Concomitantly, the endogenous 12-HETE level decreased by 35% in deficient pineals. In contrast, n–3 deficiency led to a more than 60% increase in the daytime pineal melatonin level.

In conclusion, n–3 fatty acid deficiency not only has profound effects on pineal lipid profiles but also on pineal biochemical activities. These results suggest that n–3 fatty acids may play a critical role in regulating pineal function.—Zhang, H., J. H. Hamilton, N. Salem, Jr., and H-Y. Kim. N–3 fatty acid deficiency in the rat pineal gland: effects on phospholipid molecular species composition and endogenous levels of melatonin and lipoxygenase products. J. Lipid Res. 1998. 39: 1397–1403.

Supplementary key words: polyunsaturated fatty acids, lipoxygenase, 12-hydroxyeicosatetraenoic acid, arachidonic acid, pineal, melatonin, phospholipids, n–3 fatty acid deficiency, electrospray mass spectrometry, gas chromatography/mass spectrometry

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