Objective: To study the morphological characteristics of kidney toxicity in rats when repeated intra-gastric administration of realgar in order to provide a scientific basis for safe and effective application of realgar. Method: The rats were randomly divided into four groups:control group and realgar 0.01

0.04

0.17 g·kg-1 groups. The rats were intra-gastrically treated with realgar once a day for successively 90 days

while the control group was given ultra-filtrated water. Calculatate the kidney weight and body weight index were calculated and the glucose

ketones

blood urine nitrogen and urine protein were measured and pathological change of kidney under microscope was observed at 30

60

90

120

150 days. Result: The kidney cells showed swelling

vacuolation

nuclear condensation

breakage

vasodilation and congestion after repeated intra-gastric administration of realgar ≥0.01 g·kg-1 successively 90 days or 0.17 g·kg-1 successively 60 days. Proximal convoluted tubules were seriously damaged. The lesions showed significant dose and time and toxicity relationship

blood urine nitrogen

glucose

urine protein also increased accordingly. 66.7% of the renal tubular in 0.17 g·kg-1 group showed mild swelling and degeneration at day 30 after drug withdrawal

while the other groups had no significant lesions. Conclusion: Kidneys showed severe pathologic injuries after repeated intra-gastric administration of realgar≥0.01 g·kg-1 successively 90 days or 0.17 g·kg-1 successively 60 days. The proximal convoluted tubules may be a main target of arsenic toxicity to kidneys. The lesions can gradually restored to normal after realgar withdrawal.