Abstract: Objective To evaluated the toxic effects of different concentrations of chromium-containing bedding materials on blood and organs of BALB/c nude mice and KM mice. Methods The stable different concentrations of chromium-containing bedding materials were prepared, 48 BALB/c nude mice and 48 KM mice were randomly divided into 4 groups respectively, 12 mice per group with half males and females, the dosage of chromium in control, low-dose, middle-does and high-does groups were (2.30±1.12) mg/kg, (15.50±0.71) mg/kg, (71.50±3.54) mg/kg and (347.00±35.36) mg/kg, respectively. BALB/c nude mice and KM mice were raised for 15 weeks with different bedding materials which were replaced once a week, general condition of mice were observed daily, the mice were dissected at the 15th week and the blood was collected. Besides, haematological and biochemical indexes of blood plasma, organ coefficient and organ pathology were detected. Results After 15 weeks with different bedding materials, no abnormalities and death were observed in BALB/c nude mice and KM mice, no significant differences of haematological index and organ coefficient were found between the four groups, and no abnormal anatomy was observed. In BALB/c nude mice, the alanine aminotransferase (ALT) and blood urea nitrogen (BUN) levels significantly increased in low, middle and high-dose groups, alkaline phosphatase(ALP) and creatinine (Crea) levels significantly increased in middle and high-dose groups, Triglyceride (TG) levels significantly decreased in low and high-dose groups. In KM mice groups, no significant differences of biochemical index between four groups were observed. The organ pathology showed varying degrees of focal inflammatory infiltrates and cellular swelling in the liver, inflammatory infiltrates in kedney, atrophic seminiferous tubular and decreasing corpus luteum in both BALB/c nude mice and KM mice. Conclusions Hexavalent chromium content greater than (15.50±0.71) mg/kg can cause varying degrees of toxicity in liver, kidney, testis and ovary of BALB/c nude mice and KM mice.

Key words: Chromium, Bedding materials, BALB/c nude mice, KM mice, Toxicity