Metallothionein (MT) was initially discovered from a horse kidney in 1957 as a protein that contained cadmium. Metallothionein is a heat-stable, metal-binding protein with a molecular weight of 6500 to 7000. 1) A number of physiological and biological roles have been suggested for MT, including detoxification of heavy metals, metabolic regulation of Zinc (Zn) and Copper (Cu) (two trace elements that are essential to the body), and a radical-scavenging action that is closely related to the biological defense mechanism.

The aim of this study was to determine the metabolizing activities in the liver of patients with hepatocellular carcinoma (HCC). Thin-layer chromatography autoradioluminography was used to measure metabolizing activities. Succinate-producing activity (SPA) was used as an indicator of metabolizing activity of the tricarboxylic acid (TCA) cycle in mitochondria, and diazepam-N-demethylating activity (DZ-DA), diazepam-3-hydroxylating activity (DZ-HA) and tolbutamide-methyl-hydroxylating activity (TB-HA) as indicators of drug metabolizing activities by P-450. SPA and drug-metabolizing activity of HepG2 cells were examined to compare with those of human liver specimens. Liver biopsy specimens of 30 patients and surgical specimens of eight patients with HCC were studied. SPA of HepG2 cells was as high as that of human tumor tissue, and DZ-DA, DZ-HA and TB-HA were undetectable in HepG2 cells. SPA and DZ-HA of non-tumor tissue in biopsy samples were significantly higher than those in resected liver specimens (P < 0.05). In biopsy specimens, SPA was significantly higher in tumor tissue than in non-tumor tissue (P < 0.05), and DZ-DA, DZ-HA and TB-HA were significantly lower in tumor tissue (P < 0.01). SPA was significantly higher in large tumors (>/=30 mm) than in small tumors <30 mm (P < 0.05), and TB-HA was significantly lower in large tumors than in small tumors (P < 0.01). DZ-DA and TB-HA significantly decreased with the progression of the tumor differentiation (P < 0.05). In conclusion, HCC has increased metabolizing activities of the TCA cycle and decreased drug-metabolizing activities.

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