Effects of Exposure to Cadmium on Some Endocrine Parameters in Tilapia, Oreochromis niloticus
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Effects of Exposure to Cadmium on Some Endocrine Parameters in Tilapia, Oreochromis niloticus S. Garcia-Santos • A. Fontaı´nhas-Fernandes S. M. Monteiro • J. M. Wilson
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Received: 13 September 2012 / Accepted: 17 November 2012 / Published online: 27 November 2012 Ó Springer Science+Business Media New York 2012
Abstract The cadmium impact on interrenal and thyroid functions was assessed in tilapia, Oreochromis niloticus. Fish were exposed to 25 mg L-1 of CdCl2 during 24, 48, and 96 h. Exposure to 24 and 48 h induced a significant increase in plasma cortisol levels, whereas at 96 h no differences were found. A significant and sustained decrease in plasma T3 concentrations, and an over time increase in plasma glucose, was also found in exposed fish. The results of the current study show that acute exposures to sublethal cadmium concentrations induce changes in endocrine status and carbohydrate metabolism in O. niloticus. Keywords Cadmium Tilapia Endocrine disruption HPI and HPT axis
It is widely accepted that environmental heavy metal contamination can interfere with endocrine system function in animals, including teleost fishes (Zhou et al. 2000; Hontela 2005; Oliveira et al. 2008). Cadmium is a nonessential metal that poses a serious environmental threat to aquatic organisms (McGeer et al. 2011). This pollutant is released naturally from weathering of minerals, forest fires
S. Garcia-Santos A. Fontaı´nhas-Fernandes S. M. Monteiro Centro de Investigac¸a˜o e de Tecnologias Agro-Ambientais e Biolo´gicas (CITAB), Universidade de Tra´s-os-Montes e Alto Douro, Vila Real, Portugal S. Garcia-Santos (&) DeBA, UTAD, Apartado1013, 5001-801 Vila Real, Portugal e-mail: [email protected] J. M. Wilson Centro Interdisciplinar de Investigac¸a˜o Marinha e Ambiental (CIIMAR), Porto, Portugal
and volcanic emission; however most water Cd contamination results from anthropogenic sources. The major anthropogenic sources involve atmospheric deposition, and waste waters released from zinc refining, coal combustion, mine wastes, electroplating processes, iron and steel production, and pigment, fertilizer, and pesticide use (USEPA 2001). Cd toxicity in fishes is well documented and has been found to involve several endocrine pathways important for reproduction and development. The endocrine disruption caused by Cd can occur via the hypothalamus-pituitaryinterrenal (HPI) and the hypothalamus-pituitary-thyroid (HPT) axis, however it seems that the mechanisms involved are poorly understood (Ricard et al. 1998; Lizardo-Daudt et al. 2007; Sandhu and Vijayan 2011). Cortisol is the primary circulating corticosteroid in teleosts, its release involves the coordinated activation of the HPI axis and has a vital role in maintenance of physiological homeostasis under stress conditions (Mommsen et al. 1999). Thyroid hormones are well-known to elicit diverse developmental and physiological responses in different tissues and also appear to stimulate somatic growth and metabolic functions in teleost fish. Triiodothyronine (T3) has been considered
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