The comparative toxicology of ethyl- and methylmercury
- 188 Downloads
Neurotoxicity and renotoxicity were compared in rats given by gastric gavage five daily doses of 8.0 mg Hg/kg methyl- or ethylmercuric chloride or 9.6 mg Hg/kg ethylmercuric chloride. Three or 10 days after the last treatment day rats treated with either 8.0 or 9.6 mg Hg/kg ethylmercury had higher total or organic mercury concentrations in blood and lower concentrations in kidneys and brain than methylmercury-treated rats. In each of these tissues the inorganic mercury concentration was higher after ethyl than after methylmercury.
Weight loss relative to the expected body weight and renal damage was higher in ethylmercury-treated rats than in rats given equimolar doses of methylmercury. These effects became more severe when the dose of ethylmercury was increased by 20%. Thus in renotoxicity the renal concentration of inorganic mercury seems to be more important than the concentration of organic or total mercury. In methylmercury-treated rats damage and inorganic mercury deposits were restricted to the P2 region of the proximal tubules, while in ethylmercury-treated rats the distribution of mercury and damage was more widespread.
There was little difference in the neurotoxicities of methylmercury and ethylmercury when effects on the dorsal root ganglia or coordination disorders were compared. Based on both criteria, an equimolar dose of ethylmercury was less neurotoxic than methylmercury, but a 20% increase in the dose of ethylmercury was enough to raise the sum of coordination disorder scores slightly and ganglion damage significantly above those in methylmercury-treated rats.
In spite of the higher inorganic mercury concentration in the brain of ethylmercurythan in the brain of methylmercury-treated rats, the granular layer damage in the cerebellum was widespread only in the methylmercury-treated rats. Thus inorganic mercury or dealkylation cannot be responsible for granular layer damage in alkylmercury intoxication. Moreover, histochemistry demonstrated no inorganic mercury deposits in the granular layer.
Key wordsMethylmercury Ethylmercury Neurotoxicity Renotoxicity Decomposition
Unable to display preview. Download preview PDF.
- Bakir F, Damluji SF, Amin-Zaki L, Murtadha M, Khalidi A, Al-Rawi NY, Tikriti S, Dhahir HI, Clarkson TW, Smith JC, Doherty RA (1973) Methylmercury poisoning in Iraq. Science 181: 230–241Google Scholar
- Brown AW, Aldridge WN, Street BW, Verschoyle RD (1979) The behavioural and neuropathologic sequelae of intoxication with trimethyltin compounds in the rat. Am J Pathol 97: 59–81Google Scholar
- Cappon CJ, Smith JC (1977) Gas-chromatographic determination of inorganic mercury and organomercurials in biological materials. Anal Chem 49: 365–369Google Scholar
- Chang LW, Hartman HA (1972) Ultrastructural studies of the nervous system after mercury intoxication. I. Pathological changes in the nerve cell bodies. Acta Neuropathol 20: 122–138Google Scholar
- Damluji S (1962) Mercurial poisoning with the fungicide Granosan MJ FacMed (Baghdad) 4(3): 83–103Google Scholar
- Danscher G, Schroder HD (1979) Histochemical demonstration of mercury induced changes in rat neurones. Histochemistry 60: 1–7Google Scholar
- Dunnett CW (1955) A multiple comparison procedure for comparing several treatments with a control. J Am Statist Assoc 50: 1096–1121Google Scholar
- Fang SC, Fallin E (1974) Uptake and subcellular cleavage of organomercury compounds by rat liver and kidney. Chem Biol Interact 9: 57–64Google Scholar
- Fitzhugh OG, Nelson AA, Laug EP, Kunze FM (1950) Chronic oral toxicities of mercuri-phenyl and mercuric salts. Arch In Hyg Occup Med 2: 433–442Google Scholar
- Ganther HE (1978) Modification of methylmercury toxicity and metabolism by selenium and vitamin E: possible mechanisms. Environ Health Perspect 25: 71–76Google Scholar
- Hunter D, Bomford RR, Russel DR (1949) Poisoning by methylmercury compounds. Q J Med 35: 193–213Google Scholar
- Jacobs JM (1978) Vascular permeability and neurotoxicity. Environ Health Perspect 26: 107–116Google Scholar
- Jacobs JM, Cavanagh JB, Carmichael N (1975) The effect of chronic dosing with mercuric chloride on dorsal root and trigeminal ganglia of rats. Neuropathol Appl Neurobiol 3: 321–337Google Scholar
- Jalili MA, Abbasi AH (1961) Poisoning by ethyl mercury toluene sulphonanilide. Br J Ind Med 18: 303–308Google Scholar
- Magos L (1971) Selective atomic-absorption determination of inorganic mercury and methylmercury in undigested biological samples. Analyst 96: 847–853Google Scholar
- Magos L (1982a) Mercury induced nephrotoxicity. In: Bach PH, Bonners FW, Bridges JW, Lock EA (eds.) Nephrotoxicity, assessment and pathogenesis. John Wiley & Sons, Chichester., pp 325–337Google Scholar
- Magos L (1982b) Neurotoxicity, anorexia and the preferential choice of antidotes in methylmercury intoxicated rats. Neurobehavi Toxicol Teratol 4: 643–646Google Scholar
- Magos L, Peristianis GC, Clarkson TW, Snowden RT (1980) The effect of lactation on methylmercury intoxication. Arch Toxicol 45: 143–148Google Scholar
- Magos L, Peristianis GC, Snowden RT (1978) Postexposure preventive treatment of methylmercury intoxication in rats with dimercapto succinic acid. Toxicol Appl Pharmacol 45: 463–475Google Scholar
- Siegel S (1950) Nonparametric statistics for the behavioural sciences, McGraw-Hill Kogakusha Ltd., TokyoGoogle Scholar
- Suzuki T, Miyama T, Katsunuma H (1963) Comparative study of bodily distribution in mice after subcutaneous administration of methyl, ethyl and n-propyl mercury acetates. Jon J Exp Med 33: 277–282Google Scholar
- Ulfvarson U (1962) Distribution and excretion of some mercury compounds after long term exposure. Int Arch Gewerbepathol Gewerbehyg 19: 412–422Google Scholar