| Objective:Saliva as a biological sample has a simple, non-invasive collecting method, and is easy to store, salivary analysis has become a useful tool for disease diagnosis and biological monitoring. However, the determination of arsenic concentration in saliva is just unfolding, whether salivary arsenic can be used as a new biomarker of arsenic exposure or not is still controversial. The present study aims to further verify the feasibility of salivary arsenic as a new biomarker of arsenic exposure according to the screening principle of biomarker.Methods:1. The study of the regular pattern of arsenic metabolism and excretion in saliva:(1) SD rats experiments:A single oral gavage dose of sodium arsenite (20mg/kg) was administrated to21adult male Sprague-Dawley rats. Then collected blood and saliva samples at0,1-2,4-5,7-8,11-12,17-18,23-24h for total arsenic detection.(2) The study of healthy volunteers:Four volunteers have refrained from eating any seafood for one week before and after they consumed20g seaweed at8:00am., and then collected urine and saliva samples at the time before ingesting seaweed (Oh) and1,3,6,9,12,15,18,24,36,48,60and72h after intake for total arsenic detection.2. The study of salivary arsenic and its relationship with blood arsenic and urinary arsenic of SD rats after exposure to different levels of sodium arsenite:Thirty two adult male Sprague-Dawley rats were randomly divided into four groups, the rats of control group were given oral gavage of0.9%NaCl, and other three groups were given oral gavage doses of0.2,2.0,20.0mg/kg body weight sodium arsenite. All animals were administration every other day for two weeks, then collected blood, urine, saliva and organs for total arsenic detection.3. The study in endemic arsenism areas:Combined with the previous survey data, chose70individuals in42families of four villages in endemic arsenism area in Shanyin County as the subjects of the study. The National Diagnosis Standard for Endemic Arsenism (WS/T211-2001) was used to identify and categorize the cases of arsenism during the survey. Then collected drinking water, urine and saliva for arsenic detection.4. Total arsenic detection:The total arsenic concentration in drinking water and blood were detected by Atomic Fluorescence Spectrometry (AFS-230), urinary arsenic and salivary arsenic were detected by Inductively Coupled Plasma Mass Spectrometer (ICP-MS). Besides, the urinary arsenic levels were corrected by urinary creatinine (Cr).Results:1. The study of the regular pattern of arsenic metabolism and excretion in saliva:(1) SD rats experiments:After intake of20mg/kg.bw sodium arsenite, the total arsenic concentration in blood of SD rats was increased rapidly, and reached the peak value at the1-2hour, then descended gradually. However, there was a second peak value at the7-8hour, which suggested the metabolism of arsenic in blood had an existence of enterohepatic circulation. The upward trend of salivary arsenic was more slowly than blood arsenic, and reached the peak value at the7-8hour, then descended gradually.(2) The study of healthy volunteers:After intake of seaweed, the total arsenic concentration in the urine was increased gradually, and reached the peak value at18th hour and24th hour in female and male, respectively. The change of total arsenic concentration in the saliva samples was similar to that of urine, however, the peak time of total arsenic concentration was earlier than that of urine samples. Female reached the peak value at6th hour and male reached at9th hour.2. The study of salivary arsenic and its relationship with blood arsenic and urinary arsenic of SD rats after exposed to different levels of sodium arsenite: The weight gain values of rats exposure to sodium arsenite were lower than the control group, there was a significant difference between the highest dose group and control group (p<0.05). The liver and kidney organ coefficients in the highest dose group were significantly higher than that in control group (p<0.05), pathological examination showed there were different degree injury in liver and kidney tissues of SD rats in the highest dose group. The total arsenic concentrations in saliva, blood and urine in three treatment groups were obvious higher compared with control group, furthermore, with the increase of exposure dose, the total arsenic concentrations in saliva, blood and urine were increased significantly (p<0.05). The arsenic contents in saliva were significantly correlated with blood arsenic and urinary arsenic, the correlation coefficient was0.934and0.960, respectively (p<0.01).3. The study in endemic arsenism areas:The medium value of arsenic in drinking water samples was127.22μg/L, and there were66.67%arsenic levels exceeding the drinking water standard in China for Arsenic (50μg/L), there were37individuals existed varying degrees of skin lesions among70objects. There was a significant difference of the arsenic concentration in saliva and urine exposed to different levels of arsenic in drinking water (p<0.05). There was an obvious positive association among arsenic in drinking water, saliva and urine, the correlation coefficient was0.674,0.686and0.794, respectively (p<0.01). Besides, there was a significant correlation between the skin lesions and arsenic in drinking water, saliva and urine (p<0.01).Conclusions:1. The SD rats and healthy volunteers studies both indicate that:After exposed to arsenic (inorganic or organic arsenic), the metabolism and excretion mode of arsenic in saliva are similar to that in blood and urine. The half-life of metabolism and excretion in saliva are between blood arsenic and urinary arsenic.2. After exposed to different levels of sodium arsenite, the total arsenic concentration in saliva is increased significantly with the increase of exposure dose. Even if the body exposed to a low level of sodium arsenite, the total arsenic concentration in saliva still can well reflect the exposure level of arsenic.3. The total arsenic concentration in human saliva has an obvious positive association with skin lesions and arsenic in drinking water and urine in endemic arsenism areas.4. The present study started by SD rats, healthy volunteers and crowd in endemic arsenism areas all indicate that:Salivary arsenic can well reflect the exposure level of arsenic in the body. The feasibility of salivary arsenic as a new biomarker of arsenic exposure is not only in theory, but also in the reality. Furthermore, the collection method for saliva is simple and non-invasive, and saliva has a simple composition and is easy to store, which associated with other current biomarkers can well compensate their deficiencies and screening the arsenic exposure in a better way to prevent the occurrence of arsenic poisoning. |
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