Dietary interaction between methylmercury, selenium, arsenic, and sulfur amino acids in Japanese quail

Three experiments were conducted using Japanese quail to study the effect of arsenic (As) on the detoxifying role of selenium (Se) in methylmercury (Hg) toxicity and to test the possibility that arsenic could independently modify Hg toxicity. The possible role of sulfur-containing amino acids in Hg toxicity was also investigated. Methylmercuric chloride (10 ppm) had no significant effect on weight gain of the quail. However, it seriously decreased the survival of the quail and of their offspring when they were fed the control diet for 1 week after hatching. The addition of arsenic (up to 30 ppm as NaAsO2), methionine (.3%), cystine (.3%), or their combinations did not affect the survival of mercury-fed quail or their offspring. However, the addition of selenium (6 ppm as Na2SeO3) to the mercury diet, alone or combined with cystine, methionine, arsenic, or their combination significantly prolonged the survival time of Japanese quail compared to those fed the mercury alone. Although As improved the effectiveness of Se in prolonged survival of quail given methylmercury, As decreased the effectiveness of Se in protecting the offspring of such quail. Methylmercury also decreased egg production slightly, and fertility considerably. Addition of cystine, methionine, As (up to 15 ppm), or the combination of methionine and As to the mercury-containing diet usually improved egg production. The damaging effect of mercury on fertility was corrected by supplementing the mercury diet with Se, methionine, As, or a combination of these three. This study provides evidence that As added alone in the form of arsenite has little effect on methylmercury toxicity but altered the ability of selenite to modify methylmercury toxicity. The biological mechanism of the interactions between mercury, selenium, and arsenic are not yet understood.