Influence of Selenium and Mercury Chemistries on the Progression of Cardiomyopathy in Pygmy Sperm Whales, Kogia breviceps

• Main Author: Bryan, Colleen E.
• Format: Text
• Language: unknown
• Published: MEDICA 2010
• Subjects: cardiomyopathy; molecular biology; selenium; trace elements; mercury; selenoproteins; toothed whale
• Online Access: https://medica-musc.researchcommons.org/theses/178; https://medica-musc.researchcommons.org/cgi/viewcontent.cgi?article=1178&context=theses

Pygmy sperm whales (Kogia breviceps) are the second most frequently stranded toothed whale along the U.S. Atlantic and Gulf coasts. More than half of documented cases exhibit signs of cardiomyopathy (CMP). Many factors may contribute to the development of idiopathic CMP in K. breviceps, including genetics, infectious agents, contaminants, biotoxins, and dietary intake (vitamins, selenium, mercury, and pro-oxidants). Nutritional deficiencies of selenium (Se) have been shown in mouse and bovine models to contribute to CMP. The K. breviceps diet, consisting mainly of squid, imparts a high dose of mercury (Hg), which requires detoxification, and polyunsaturated fatty acids (PUFAs) that require effective antioxidant biochemistry to regulate free radical formation. This study assesses trace elements in K. breviceps at various stages of CMP progression using fresh frozen liver and heart samples collected from individuals that stranded along the coasts of MA, VA, NC, SC, GA, and FL between 1991-2007. Standard addition calibration and collision cell inductively coupled plasma mass spectrometry (ICP-MS) were employed for total Se analysis and pyrolysis atomic absorption (AA) was utilized for total Hg analysis to examine if the Se/Hg detoxification pathway inhibits the bioavailability of Se. Double spike speciated isotope dilution gas chromatography ICP-MS was utilized to measure methyl Hg and inorganic Hg. Due to the important role Se can play in antioxidant biochemistry and protein formation, selenoprotein and small molecule Se species profiles were examined by multi-dimension liquid chromatography ICP-MS detection, and selenoprotein identification was performed by liquid chromatography electrospray tandem mass spectrometry (ESI-MS/MS). Immunoblot detection and colorimetric assays were used to assess overall protein oxidation status. Data collected on trace elements, selenoproteins, and oxidative status were evaluated in the context of animal life history and other complementary histological information to gain insight into the biochemical pathways contributing to the development of CMP in K. breviceps. Cardiomyopathy was only observed in adult pygmy sperm whales, predominantly in male animals. Both Hg and Se concentrations increased with animal age and progression of cardiomyopathy. Animals with cardiomyopathy had greater overall protein oxidation. Selenium protein patterns, such as metallothioneins, were different between animals with no pathological findings and those with cardiomyopathy, indicating that Se protein expression is altered with the disease state in pygmy sperm whales.