The isolated rat liver cells were dispersed in the medium under various conditions to observe the behavior of the leakage of the enzymes from liver cells. Furthermore, the hepatic artery of rat was ligated to examine the effect of hypoxia on the enzyme leakages from liver into the circulation. The alterations of the enzymes in serum and liver tissue were also examined using rats with liver cirrhosis induced by CCl(4). The enzymes assayed were Glutamate dehydrogenase (GLD), Transaminases (GOT and GPT), Isocitrate dehydrogenase (ICD) and Glucose-6-phosphatase (G-6-Pase). The following results were obtained. 1. When the liver cells were dispersed in the medium, there was a marked leakage of such activities as GOT and ICD, whereas GLD almost completely retained within the cells. 2. After incubating the isolated cells in the medium under hypoxia, an extremely increased leakage of GLD was observed. The leakage of other enzymes measured, however, was little influenced by hypoxia. Similar results were obtained with dinitrophenol. 3. The ligation of hepatic artery of rat caused the earliest and most remarkable increase of the serum GLD, whereas the rise of GOT was moderate. The serum levels of GPT, ICD and G-6- Pase did not changed essentially compared with control. 4. Despite of the marked elevation of the serum GLD, ADP/O ratio of the mitochondria of the hepatic cells was not effected by the ligation of the hepatic artery. This result suggests that the increase of the serum GLD does not always imply the irreversible damages of the hepatic mitochondria. 5. The activities of GLD and G-6-Pase within the experimentally induced cirrhotic liver of rat showed a remarkable diminution, whereas these activities in serum increased markedly.