[Study of mercury cumulation in Cinnabar-treated rats]

Abstract

Objective: To investigate the mercury cumulation following single dose or long-term use of Cinnabar to rats.

Method: The Cinnabar which was used in the study contains 98% insoluble mercuric sulfide (HgS) and 21.5 mg x kg(-1) soluble mercuric compounds. Two separate experiments were performed: (1) Tweenty-eight fasting SD rats were orally given a single dose of Cinnabar at the dose of 0.8 g x kg(-1) and the other four rats were given ultra-filtrated water served as control group. Blood, livers, kidneys and brains of four rats were taken out at 0.5, 1, 2, 4, 8, 16, 36 h respectively after treatment. Mercury quantity of each organ or blood sample was measured. (2) Forty SD rats were randomly divided into four groups: control group and Cinnabar 0.1, 0.4, 0.8 g x kg(-1) groups, each group containing 5 females and 5 males. The rats were intra-gastrically treated with Cinnabar once a day for successively 90 days, while the control group was given ultra-filtrated water. Mercury contents in blood, livers, kidneys and brain of each rat were measured at 16 h of fasting after last dosing.

Result: Mercury contents of blood, liver, kidney and brain increased slightly after single dosing of Cinnabar at dose of 0.8 g x kg(-1), with the order from high to low liver > blood > brain > kidney. Whereas 90-day oral treatment of Cinnabar led to significant cumulation of mercury in organs but not in blood. Kidney' s cumulation of mercury was much higher than any other tested organs and blood. Brain's mercury cumulation was also very high. The contents of mercury in kidney and brain of 0.8 g x kg(-1) group (total intake of soluble mercury within 90 days was 1 548 microg x kg(-1)) were respectively 71.2 and 27.4 times higher than control group. Even though in the lowest dose 0.1 g x kg(-1) group (total intake of soluble mercury 194 microg? kg(-1)), the mercury cumulation folds in kidney and brain were 16.77 and 20.43 respectively. However, liver got lower mercury cumulation than kidney and brain, which led to only 2 folds mercury cumulation at dose of 0.8 g x kg(-1). Our previous study showed that 90-day administration of Cinnabar at the dose > or = 0.1 g x kg(-1) (total intake of soluble mercury 194 microg x kg(-1)) could cause pathological changes in kidney and liver, indicating both were the toxicity targets for Cinnabar. Those manifested that liver could be more sensitive than kidney to mercury. Though brain got 20 times mercury cumulation after 90 day treatment, the animals showed no abnormal signs in general behavior and brain histomorphology,which indicated that rat brain was not sensitive to mercury.

Conclusion: Soluble mercury in Cinnabar can be absorbed causing high cumulated in some organs, such as kidney and brain after long-term use of Cinnabar. Liver had also mercury cumulation, but was much lower than kidney. Total intake of soluble mercury for > or = 194 microg x kg(-1) within 90 days could cause toxicosis by mercury cumulation.