INFLUENCE OF DIETARY SELENIUM ON THE DISPOSITION OF ARSENATE IN THE FEMALE B6C3F(1) MOUSE

Interactions between arsenic (As) and selenium (Se) at the metabolic l evel are multifaceted and complex. These interactions are of practical significance because populations in various parts of the world are si multaneously exposed to inorganic As in drinking water and Se mainly i n the diet at varying levels. The primary goal oi this study was to in vestigate whether differing dietary Se status would alter the profile of urinary metabolites or their time course for elimination after expo sure to arsenate [As(V)]. Weanling female B6C3F(1) mice were maintaine d for 28 d on either a control diet of powdered rodent meal sufficient in Se (A, 0.2 ppm) or Torula yeast-based (TYB) diets deficient (B, 0. 02 ppm Se), sufficient (C, 0.2 ppm Se), or excessive (D, 2.0 ppm Se) i n Se; mice then received by oral gavage 5 mg (As)/kg as sodium [As-73] arsenate. The time course for elimination of total arsenic and metabo lites in urine was measured over a 48-h period, and total arsenic was determined in feces and tissues at 48 h. Mice on the Se excess diet ex creted a significantly higher percentage of urinary As as inorganic As , with a significantly decreased ratio of organic to inorganic As comp ared to Se-sufficient mice, suggesting that As methylation was decreas ed. Mice on the Se-deficient diet appeared to eliminate As(V), arsenit e, and dimethylarsinic acid (DMA) in urine more slowly than Se-suffici ent mice; however, further studies are required to confirm this findin g. Mice on the Se-sufficient meal diet (A) excreted significantly less (by percent) arsenate-derived radioactivity in urine and more in fece s compared to mice on the Se-sufficient TYB diet (C), with total elimi nation being similar for both groups. This indicates that mice on the meal diet absorbed significantly less As(V) than mice on the NE diet, and this may be due to more fiber or ''bulk'' in the meal diet. This f inding emphasizes the importance of considering dietary composition wh en interpreting and comparing As disposition studies. Overall this stu dy provides suggestive evidence that dietary Se status alters As metab olism and disposition. This indicates that dietary Se status may be an issue that should be considered in the design and interpretation of e pidemiologic studies.