Dietary Fish Oil Reduces Pacemaker Current and Heart Rate in Rabbit

Heart Rhythm. 2009 Oct;6(10):1485-92. doi: 10.1016/j.hrthm.2009.07.024. Epub 2009 Jul 16.

Abstract

Background: Omega-3 polyunsaturated fatty acids (omega3-PUFAs) from fish oil (FO) reduce heart rate in humans. The mechanism underlying this cardioprotective effect of FO is unknown.

Objective: We studied the effects of an FO diet on heart rate, pacemaker activity, and pacemaker current (I(f)) in sinoatrial node (SAN) cells.

Methods: Rabbits were fed a diet enriched with 2.5% (w/w) FO or 2.5% high oleic sunflower oil (SO) as control for 3 weeks. Heart rate was measured in Langendorff-perfused hearts. Pacemaker activity and I(f) were recorded using the perforated patch-clamp technique in isolated SAN cells.

Results: In SAN cells, the FO diet reduced I(f) density by approximately 30%, without changes in its voltage dependence, reversal potential, (de)activation kinetics, and sensitivity to beta-stimulation. Dietary FO significantly prolonged the cycle length in both isolated perfused hearts (337 +/- 8 [mean +/- SEM, n = 8] vs. 301 +/- 9 ms [n = 8]) and single cells (363 +/- 20 [n = 19] vs. 276 +/- 8 ms [n = 22]). In single cells, dietary FO significantly decreased the diastolic depolarization rate by 33% and prolonged the action potential by 27%, whereas other action potential parameters were unaltered. I(f) blockade experiments substantiated that the reduced diastolic depolarization rate in the FO group was partially caused by the I(f) density reduction.

Conclusion: An FO diet prolongs the sinus cycle length because of, at least in part, a reduction in I(f) density. Our results explain FO-induced heart rate reduction and suggest FO as an alternative or adjunct to I(f)-lowering drugs.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Biological Clocks / drug effects*
  • Dietary Fats, Unsaturated / pharmacology*
  • Fish Oils / pharmacology*
  • Heart Rate / drug effects*
  • Helianthus
  • In Vitro Techniques
  • Male
  • Oleic Acid / pharmacology
  • Rabbits
  • Sinoatrial Node / cytology
  • Sinoatrial Node / drug effects

Substances

  • Dietary Fats, Unsaturated
  • Fish Oils
  • Oleic Acid