The effect of omega-3 polyunsaturated fatty acids enriched diet on the contractile function, structure, Ca2+ handling and electrophysiology in the rat heart**

Introduction. Omega-3 polyunsaturated fatty acids (ω-3 PUFA) are essential fatty acids that cannot be synthesized by mammals and must be delivered with food. Epidemiological observations suggest that supplementation of ω-3 PUFA reduces cardiovascular mortality, although results of clinical trials and animal studies are highly variable and inconsistent. Aim. The aim of the study was to examine cardiovascular effects of ω-3 PUFA supplementation in healthy rats. Eicosapentanoic acid (EPA) and docosahexanoic acid (DHA), the two most commonly used ω-3 PUFAs, were used. Material and methods. Rats were fed with normal chow or EPAor DHA-enriched diet for 4 weeks. Epicardial monophasic action potentials (MAPs) were recorded, cardiomyocyte Ca2+ handling was assessed and eachocardiographic imaging was performed before and after 4 weeks of feeding. Results. Neither EPA nor DHA affected left ventricular (LV) ejection fraction, wall thickness or diameters, indicating that 4 weeks of feeding had no effect on LV structure and function. While EPA enriched diet had no impact on intracellular Ca2+ handling, DHA-rich diet significantly increased amplitude of Ca2+ transient and SR Ca2+ content. Neither EPA nor DHA affected action potential duration, however EPA mildly increased action potential amplitude. Conclusions. This indicates that ω-3 PUFAs are safe for the cardiovascular system, but the above mentioned cellular effects may be considered arrhythmogenic under specific conditions.