The views and policy of the Japanese control authorities on the three Rs.

NIH Japan has tested and regulated the three Rs of animal experiments in the development and control of biological products in a stepwise manner. (1) The number of monkeys was reduced from 108 to 72 for the neurovirulence test of OPV in each type, since paralysed monkeys inoculated intraspinally revealed a linear relationship between average scores of the lumbar lesion and cumulated paralysis occurrence ratio (%). (2) Rabbits for the pyrogen test were replaced by the endotoxin test for PPF, albumin and interferon products. The endotoxin is measured by the parallel line assay method using both turbidimetric kinetic and colorimetric methods. (3) Histopathological examination was introduced to the abnormal toxicity test as a refinement. Mean body weight loss of two guinea pigs inoculated with five ml. of an albumin product in each was far below the mean weight of pooled guinea pigs used (P < or = 0.01) and appeared repeatedly. The histopathological examination showed focal necrosis in the liver. This finding was suggestive of the presence of endotoxin in the product. The product contained 0.1 EU/ml of endotoxin. The same amount of the reference endotoxin produced a similar change in guinea pigs. The mechanism of the liver cell damage by endotoxin has been investigated by an in vitro method.