N-3 POLYUNSATURATED FATTY ACID SUPPLEMENTATION IN CARDIAC MYOCYTES AND CELL SIGNALLING
S.S.D. Nair*, J. Leitch, M.L. Garg.
University of Newcastle and Department of Cardiology, John Hunter Hospital, New South Wales.
Dietary n-3 polyunsaturated fatty acids (n-3PUFA) from fish oil has been shown to prevent ischaemia induced arrhythmias in small experimental animals and neonatal cardiac myocytes. One of the potential mechanisms to explain the anti-arrhythmic effect of n-3PUFA is the modification of cell membrane phospholipids, particularly calcium release via the second messenger channels. This study was undertaken to investigate this mechanism after n-3PUFA supplementation in adult porcine cardiac myocytes.
Cardiac myocytes isolated from the ventricles of adult pigs were incubated for 24 hours in media supplemented with the n-3 fatty acids, eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) and the n-6 fatty acid arachidonic acid (AA). Unsupplemented cells were treated as controls. The modified cells were then labelled with [3H]myo-inositol for 48 hours and stimulated with epinephrine and phenylephrine. The [3H] inositol phosphates were extracted and separated by column chromatography.
In EPA and DHA treated myocytes, the levels of both the second messengers, IP3 and IP4 were significantly reduced (p<0.05) after stimulation compared to AA and control cells. To compare the in vitro and in vivo effects of n-3PUFA on cell signalling, cardiac myocytes were isolated from pigs prefed a diet containing 5% w/w fish oil (MaxEPA) for 6 weeks. In these cardiac myocytes, the levels of IP3 and IP4 after stimulation were significantly less (p<0.05) than the levels in beef tallow fed animals.
This study thus effectively demonstrates that both in vitro and in vivo, fish oil modulates phospholipase C mediated inositol lipid cycle and the generation of second messengers.
