Subchronic mercury exposure in coturnix and a method of hazard evaluation

Abstract

AbstractThe sublethal toxicity of inorganic (HgCl2) and organic (CH3HgCl) mercury chloride was studied in coturnix (Coturnix japonica) by feeding them mercuric compounds (CH3HgCl at concentrations of 0.125,0.5,2 and 8 ppm; HgCl2 at 0.5, 2, 8 and 32 ppm) in ad libitum diets from hatching to adulthood. Differences of response to the mercurials were compared on the basis of selected indicator enzymes and plasma chemistries. Comparisons of response to equivalent concentrations of the two mercurials and dose‐response relationships were made at 1,3,5,7 and 9 weeks. Changes of activity were detected for brain acetylcholinesterase (AChE) and the plasma enzymes aspartate aminotransferase (ASAT), butyrylcholinesterase (BChE), lactate dehydrogenase (LDH) and ornithine carbamoyl transferase (OCT). Changes of ASAT, LDH and OCT were then quantified by probit analysis and the mercurials were compared through their median effective concentrations (EC50). This quantal procedure was based on the establishment of normal control values for each enzyme and then classifying mercury‐treated outliers (more than ± 2 SD) as respondents. The EC50 values at 9 weeks for ASAT, LDH and OCT, respectively, were 9, 3 and 63 ppm for HgCl2, and 5, 1 and 4 ppm for CH3HgCl. These results provided the basis for two hazard indices that were calculated by dividing the EC50 into the oral LD50 and the 5‐d dietary LC50. Mercury also had contradictory effects on gonadal maturation in both sexes.