Subcellular distributions of trace elements (Cd, Pb, As, Hg, Se) in the livers of Alaskan yelloweye rockfish (Sebastes ruberrimus)

Abstract

Yelloweye rockfish (Sebastes ruberrimus) is an extremely long-lived species (up to ∼120 years) of fish, which inhabits the coastal waters of Alaska. Due to their long lifespans, yelloweye are known to accumulate high levels of mercury, and potentially other trace elements, in their tissues. Relatively little is known about the subcellular distribution of trace elements in the tissues of yelloweye rockfish; such information can provide important insights into detoxification/toxicity mechanisms at the subcellular level. To address this, we collected yelloweye rockfish (n = 8) from the eastern coast of Prince of Wales Island, Alaska in 2014. We determined the subcellular partitioning of trace elements (cadmium (Cd), lead (Pb), arsenic (As), total mercury (Hg), and selenium (Se)) in yelloweye livers with a partitioning procedure designed to separate liver cells into putative metal-sensitive fractions (cytosolic enzymes, organelles) and detoxified metal fractions (metallothionein or metallothionein-like proteins and peptides, granule-like structures) using differential centrifugation, NaOH digestion, and heat denaturation steps. The resulting fractions were then analyzed for total Hg with a direct Hg analyzer and for trace element concentrations by inductively coupled plasma-mass spectrometry (ICP-MS). For Cd, Pb, and As, the greatest contributions were found in the detoxified fractions, whereas the majority of total Hg was found in sensitive fractions. Selenium, an essential trace element, was distributed to a similar degree between the sensitive and detoxified compartments. Results indicate that although yelloweye sequestered and immobilized potentially toxic elements in detoxified fractions, the extent of binding differed among elements and followed the order: Cd > As > Pb > Hg. In yelloweye rockfish livers, the accumulation of non-essential elements at sensitive sites could lead to deleterious effects at the subcellular level, which should be evaluated in future studies.