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ผู้เขียน หัวข้อ: Chronic effects of copper exposure versus endocrine toxicity  (อ่าน 2224 ครั้ง)
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« เมื่อ: มีนาคม 30, 2010, 08:43:56 PM »

Chronic effects of copper exposure versus endocrine toxicity:two sides of the same toxicological process?
Richard D. Handy*
School of Biological Sciences, University of Plymouth, Drake Circus, Plymouth PL4 8AA, UK

Received 8 August 2002; received in revised form 18 December 2002; accepted 14January 2003
Comparative Biochemistry and Physiology Part A 135 (2003) 25–38

Abstract
Chronic sub-lethal exposure to copper (Cu) causes a series of cellular and physiological changes in fish that enable the animal to survive. Copper is also an endocrine disrupting metal in the aquatic environment, and has a number of normal neuro-endocrine roles in vertebrates. This paper explores whether the chronic effects of Cu exposure can be explained by the effects of Cu on neuro-endocrine functions in fish. Chronic Cu exposure involves complex physiological adjustments in many body systems, including increased oxygen consumption, reduced mean swimming speed, upregulation of ionic regulation, decreasing lymphocyte levels and increasing neutrophils, altered immunity, modulation of Cu-dependent and independent enzyme activities, and proliferation of epithelial cells in gills or intestine. These responses
can occur with exposure via the food or the water and can be rationalised into three major categories: (1) up-regulation of enzymesymetabolism (2) altered haematopoietic responses and (3) altered cellularity (cell type, turnover or size) in tissues. Some of these responses can be explained by stimulation of general stress responses, including the adrenergic response and stimulated cortisol release via the hypothalamic–pituitary–interrenal axis. This can occur despite evidence of vacuolation and foci of necrosis in the brain, and increased macrophage activity, in the kidney of fish exposed to dietary Cu. In addition to generic stress responses, Cu regulates specific neuro-endocrine functions, including the loss of
circadian rhythm during dietary Cu exposure that involves the failure to respond to circulating melatonin and a loss of circulating serotonin. We conclude that the chronic physiological effects of Cu and apparent endocrine disrupting effects of Cu are two sides of the same toxicological process.

 2003 Elsevier Science Inc. All rights reserved.

Keywords: Copper; Chronic exposure; Stress response; Cortisol; Catecholamines; Endocrine disruption; Brain pathology; Serotonin;
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