Metallothionein (MT) is a low molecular weight and cysteine-rich protein that binds to several heavy metals. The suggested functions of MT are detoxification of heavy metals, maintenance of trace element homeostasis, and scavenging of free radicals via the thiol groups present in the protein.1,2) Hepatocellular carcinoma (HCC) is one of the most common human tumors that occurs globally, and generally develops from chronic hepatitis (CH) and liver cirrhosis (LC). [3][4][5] It is, therefore, very important to detect and evaluate the progressing state of chronic hepatic disorder in order to diagnose the diseases.We have previously reported that abnormal accumulations of both copper (Cu) and total MT occur in the livers of Long Evans Cinnamon (LEC) rats and that these accumulations are directly related to the development of jaundice and hepatoma.6-10) Similar observations have been reported with regard to the livers of HCC patients, although the concentrations of metals and total MT accumulations differed among the studies. [11][12][13][14] Many researchers have reported that the serum copper/zinc (Cu/Zn) ratio is sufficiently sensitive to diagnose various diseases. [15][16][17] The serum Cu/Zn ratio in the patients with different hepatic diseases has been confirmed to be significantly higher than that of patients without hepatic disorders (Ctrl). [18][19][20] However, during our study, some patients with congestive heart failure, diabetes mellitus, and hypertension exhibited markedly high Cu/Zn ratio, indicating that the ratio could not be considered selective for diagnosing the diseases. On the other hand, we also reported that Cu concentrations in the human liver cytosol increased with the development of HCC. [18][19][20] The increase in Cu concentrations in the hepatic tissues were due to the distribution of Cu in MT rather than in superoxide dismutase (SOD) in the hepatic tissues.21) Based on these observations, we attempted to determine whether monitoring of MT isomers and metal concentrations in human liver is a better approach for diagnosing human liver disorder.It is well known that MT occurs in several isoforms, 22) among which MT-1 and MT-2 are induced in most organs by specific stimuli such as exposure to toxic metals and glucocorticoids. 23) Although the biological functions and physiological role of MT are not yet known, based on the results of the analysis of hepatic MT-1 and MT-2 in LEC rats we recently proposed that MT-1 is related to the metabolism or detoxification of toxic metals such as cadmium, and, MT-2 is responsible for the homeostasis of essential metals such as Cu.24) Since the pathophysiological feature of hepatic disorders in LEC rats has been reported to be very similar to that of human hepatic diseases involving HCC, 25,26) we attempted to determine MT-1 and MT-2 in the liver cytosol of humans by using a capillary zone electrophoresis (CZE). Previously, It is desirable to diagnose hepatocellular carcinoma (HCC) in the early stages during its development since its treatment is usually d...