Hormone, vitamin and contaminant status during the moulting/fasting period in ringed seals ( Pusa [ Phoca] hispida) from Svalbard

• Published in: Comparative biochemistry and physiology. Part A, Molecular & integrative physiology Molecular & integrative physiology, 2010, Vol.155 (1), p.70-76
• Main Authors: Routti, Heli, Jenssen, Bjørn Munro, Lydersen, Christian, Bäckman, Christina, Arukwe, Augustine, Nyman, Madeleine, Kovacs, Kit M., Gabrielsen, Geir Wing
• Format: Article
• Language: English
• Subjects: Animals; Biomarkers; Calcitriol; Deiodinase; Fasting - blood; Fasting - metabolism; Fasting - physiology; Female; Health Status; Hormones - analysis; Hormones - blood; Hormones - metabolism; Liver - chemistry; Liver - metabolism; Male; Molting - genetics; Molting - physiology; Phoca - blood; Phoca - genetics; Phoca - metabolism; Phoca - physiology; Retinoic acid receptor; Seasons; Svalbard; Thyroid hormone; Thyroid hormone receptor; Thyroid Hormone Receptors beta - genetics; Thyroid Hormone Receptors beta - metabolism; Vitamin A; Vitamin E; Vitamins - analysis; Vitamins - blood; Vitamins - metabolism; Water Pollutants, Chemical - analysis; Water Pollutants, Chemical - blood
• ISSN: 1095-6433; 1531-4332
• DOI: 10.1016/j.cbpa.2009.09.024

This study investigates the potential effects of moulting, and the concomitant period of fasting undertaken by ringed seals, on hormone, vitamin and contaminant status in adult animals in a population from Svalbard, Norway, which has relatively low contaminant levels. Concentrations of circulating total and free thyroxine and triiodothyronine, circulating and hepatic vitamin A, hepatic persistent organic pollutants and their circulating hydroxyl metabolites were higher in moulting seals compared to pre-moulting seals. The opposite trend was observed for body condition, circulating calcitriol levels and hepatic mRNA expression of thyroid hormone receptor β. No differences were observed for circulating or hepatic vitamin E levels or hepatic mRNA expressions for deioidinase 1 or 2, or retinoic acid receptor α between the two seal groups. The observed differences are likely the result of increased metabolic rates required during moulting to maintain thermal balance and replace the pelage, in combination with mobilization of lipid soluble compounds from blubber stores during the fasting period that is associated with moulting. The present study shows that contaminant levels and their relationships with physiological or endogenous variables can be highly confounded by moulting/fasting status. Thus, moulting status and body condition should be taken into consideration when using variables related to thyroid, calcium or vitamin A homeostasis as biomarkers for contaminant effects.