Toxicological studies on bestatin. II. Subacute toxicity test and recovery study in beagle dogs

Subacute toxicity and its recovery of bestatin (NK421) was studied on both sexes of 34 Beagle dogs. At dose levels of 600, 240, 96 and 38.4 mg/kg, NK421 was administered orally to dogs for 90 successive days. The control group was treated orally with 2 g/dog of corn starch. Each group was constituted of 3 males and 3 females, and 2 males and 2 females were added to the 240 mg/kg group for the recovery test for 35 days. As general symptoms, loss of appetite, vomiting, abnormal feces (loose stool, diarrhea, mucous stool), eye mucus, decoloration of the visible mucous membrance and unkempt fur were observed slightly and almost dose-dependently in the group dosed with more than 96 mg/kg. Body weight decreased with the passage of time in the 600 and 240 mg/kg groups, but no death appeared in any group. In correlation with general signs, slight anemia was seen hematologically, and the increased alkaline phosphatase activity and the decreased albumin ratio in serum protein fraction were observed biochemically. The slight abnormal findings of bone marrow, spleen and liver were also demonstrated histopathologically. All the above findings disappeared during the recovery period. The maximum non-toxic dose of NK421 in this study is estimated to be 38.4 mg/kg in dogs.