Scientists from Stanford University and the National Oceanic and Atmospheric Administration (NOAA) have discovered that crude oil interferes with fish heart cells. The toxic consequence is a slowed heart rate, reduced cardiac contractility and irregular heartbeats that can lead to cardiac arrest and sudden cardiac death.
The research, published in the Feb. 14 issue of Science, is part of the ongoing Natural Resource Damage Assessment of the April 2010 Deepwater Horizon oil spill.
While crude oil is known to be cardiotoxic to developing fish, the physiological mechanisms underlying its harmful effects were unclear. Stanford and NOAA scientists studying the impact of crude oil from the Deepwater Horizon spill on tuna discovered that it interrupts the ability of fish heart cells to beat effectively.
Crude oil is a complex mixture of chemicals, some of which are known to be toxic to marine animals. Past research has focused in particular on "polycyclic aromatic hydrocarbons" (PAHs), which can also be found in coal tar, creosote, air pollution and stormwater runoff from land. In the aftermath of an oil spill, PAHs can persist for many years in marine habitats and cause a variety of adverse environmental effects.
The researchers report that oil interferes with cardiac cell excitability, contraction and relaxation - vital processes for normal beat-to-beat contraction and pacing of the heart. Their tests revealed that very low concentrations of crude oil disrupt the specialized ion channel pores - where molecules flow in and out of the heart cells - that control heart rate and contraction in the cardiac muscle cell.
This cyclical signaling pathway in cells throughout the heart is what propels blood out of the pump on every beat. The protein components of the signaling pathway are highly conserved in the hearts of most animals, including humans.