A latest study on tuna found that crude oil can interrupt a key pathway found in the hearts of fish and other marine animals. The 2010 Deepwater Horizon oil spill exposed tuna and several marine organisms to high levels of crude oil.
Researchers at Stanford University and the National Oceanic and Atmospheric Administration (NOAA), found that the crude oil can change the signalling mechanism of the heart.
The 2010 Deepwater Horizon oil spill released four million barrels of oil during peak spawning season for the Atlantic bluefin tuna.
Researchers in the present study set out to find the specific cause for the elevated heart problems in fish near oil spills. The study also explains why humans exposed to air pollution have increased risk of heart attacks.
Past research on pollution and heart problems usually focused on a chemical called "polycyclic aromatic hydrocarbon" (PAHs). These hydrocarbons can be found in coal tar and air pollution and can linger in animals for a long time, disturbing several biological processes. Research on animals has shown that PAHs affect fertility and the ability to fight infection.
In the current study, the experts found that oil interferes with key mechanisms - "cardiac cell excitability, contraction and relaxation"- which can lead to irregular heartbeat.
Exposure to crude oil can lead to changes in specialized ion channel pores. Ions move in and out of these channels, which leads to contraction of heart muscle cells. This signalling pathway is the reason that the heart beats and helps supply blood throughout the body.
Researchers found that the oil specifically affects potassium ion movements, which leads to delays in contraction.
"The ability of a heart cell to beat," explained Barbara Block, a professor of marine sciences at Stanford, "depends on its capacity to move essential ions like potassium and calcium into and out of the cells quickly. This dynamic process, which is common to all vertebrates, is called 'excitation-contraction coupling.' We have discovered that crude oil interferes with this vital signaling process essential for our heart cells to function properly."
For the study, researchers isolated cardiac cells and bathed them with low dose crude oil concentrations. They then used electro-physiological techniques to record ion movements in the cells to see which proteins were most affected by the oils.
"The normal sequence and synchronous contraction of the heart requires rapid activation in a coordinated way of the heart cells," Block said in a news release. "Like detectives, we dissected this process using laboratory physiological techniques to ask where oil was impacting this vital mechanism."
The study is published in the journal Science.
The Deepwater Horizon spill not only affected hearts of tuna, but also led to lung damage and hormonal changes in several dolphins.