Dietary fish oil prevents asynchronous contractility and alters Ca2+ handling in adult rat cardiomyocytes

This study examined the effects of dietary incorporation of n-3 polyunsaturated fatty acids (PUFAs) into cardiac membrane phospholipids on Ca2+ handling (using Fura-2) and arrhythmic contractility in electrically-stimulated, adult rat ventricular cardiomyocytes. Dietary lipid supplementation with fish oil (FO) for 3 weeks significantly increased the proportion of total n-3 polyunsaturated fatty acids (in particular, docosahexaenoic acid) in ventricular membrane phospholipids compared with a saturated fat (SF) supplemented diet (26.2 ± 0.9% vs 6.9 ± 0.9%, respectively, P < 0.001). Cardiomyocytes isolated from the FO group were significantly (P < 0.001) less susceptible to isoproterenol-induced arrhythmic contractile activity compared with the SF group over a range of isoproterenol concentrations. Isoproterenol (0.5 μM) stimulation increased end-diastolic and systolic [Ca2+]i to a similar extent in both groups. The time constant of Ca2+ transient decay was significantly increased in the FO group compared with the SF group (98.4 ± 2.8 ms, n = 8 and 86.9 ± 2.1 ms, n = 8, P < 0.01, respectively). The effect of dietary n-3 PUFA incorporation into membrane phospholipids was not associated with changes in sarcoplasmic reticulum Ca2+ content (measured by rapid application of caffeine) or membrane fluidity. The increase in the time constant of decay of Ca2+ transients following dietary supplementation with FO may indicate altered functioning of the sarcolemmal Na+-Ca2+ exchanger by n-3 PUFA incorporation into membrane phospholipids.