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Crude Oil Impairs Cardiac Excitation-Contraction Coupling in Fish

Crude oil from the Deepwater Horizon spill is cardiotoxic to tuna species that spawn in the Gulf of Mexico. Crude oil is known to disrupt cardiac function in fish embryos. Large oil spills, such as the Deepwater Horizon (DWH) disaster that occurred in 2010 in the Gulf of Mexico, could severely affect fish at impacted spawning sites. The physiological mechanisms underlying such potential cardiotoxic effects remain unclear. Here, we show that crude oil samples collected from the DWH spill prolonged the action potential of isolated cardiomyocytes from juvenile bluefin and yellowfin tunas, through the blocking of the delayed rectifier potassium current (IKr). Crude oil exposure also decreased calcium current (ICa) and calcium cycling, which disrupted excitation-contraction coupling in cardiomyocytes. Our findings demonstrate a cardiotoxic mechanism by which crude oil affects the regulation of cellular excitability, with implications for life-threatening arrhythmias in vertebrates. Oil Is Bad for the Heart Crude oil, which commonly makes up the largest proportion of spilled oil, is cardiotoxic to fish embryos. To better understand the processes involved, Brette et al. (p. 772) exposed captive young tuna to oil samples collected from the Deep Water Horizon spill site to determine the mode of cardiotoxicity. Crude oil prolonged the action potential of cardiomyocytes and disrupted the excitation-contraction coupling in these cells, functionally disrupting cellular excitability and creating the potential for cardiac arrhythmias. Such cardiac impacts may be more broadly distributed in vertebrates exposed to crude oil.