Effects of acute exposure to mercury chloride and methylmercury on plasma cortisol, T3, T4, glucose and liver glycogen in rainbow trout (Oncorhynchus mykiss)

Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to mercury chloride HgCl2 (28 and 112 mu g/l Hg2+), and to methylmercury chloride CH3HgCl (6, 12 and 24 mu g/l Hg) for 4, 72 and 168 h to determine the effects of sublethal doses of these compounds on the hypothalamo-pituitary-interrenal and the hypothalamo-pituitary-thyroid axes. Exposure to both mercurial compounds significantly increased plasma cortisol, plasma thyroxine (T4) and plasma glucose levels. Similar trends were observed in plasma triiodothyronine (T3) levels. A decrease in liver glycogen reserves was detected after 1 week of exposure to 6 mu g/l CH3HgCl. Our results indicate that both mercurial compounds stimulate the pituitary-interrenal and the pituitary-thyroid axis and modify the carbohydrate metabolism in juvenile rainbow trout, and that the organic mercury CH3Hg+ is a more potent chemical stressor than the inorganic Hg2+.