CATALASE ACTIVITY IN ERYTHROCYTES FROM COLON AND GASTRIC-CANCER PATIENTS - INFLUENCE OF NICKEL, LEAD, MERCURY, AND CADMIUM

Catalase (CAT) is an enzyme that is involved in antioxidant defense, c ell growth, and is possibly associated with tumoral processes. In this paper, the results of experiments designed to determine the influence of metallic carcinogens such as nickel (Ni), lead (Pb), mercury (Hg), and cadmium (Cd), on CAT activity are reported. CAT activity was meas ured in erythrocytes from three groups: a group of colon cancer patien ts, a group of gastric cancer patients before clinical treatment, and a control group of healthy blood donors. Concentrations of this enzyme are significantly higher than controls in the colon cancer group, but lower in gastric neoplasia. By generating highly reactive oxygenated species, Ni, Pb, Hg, and Cd alter catalase activity. Solutions of Ni, Cd, and Pb at 0.2 mM concentrations inhibit CAT activity in colon canc er, but increase it in gastric neoplasia. Hg activates CAT in colon ca ncer, and causes a slightly increased activity in gastric cancer. No c omplete deactivation of the enzyme was observed.