DNA fragmentation in some organs of rats and mice treated with cycasin

Cycasin (methylazoxymethanol-beta-D-glucoside) is carcinogenic in several animal species. It produces a variety of malignant tumours, mainly in the liver of mice, and in the liver, kidney and large intestine in rats. It does not appear to be mutagenic in the Ames test, even in the presence of liver microsome fraction, and it is among those carcinogens (less than 10%) ranked as "false negatives" in this test. The ability of cycasin to damage in vivo liver, kidney, lung and colonic DNA of Wistar rats and C57BL/L mice was investigated by means of alkaline elution technique. Oral single-dose administration of cycasin, in the range of 50-400 mg/kg body weight, produced in the rat a clearly evident dose-dependent DNA fragmentation in the liver, and less marked damage to DNA from kidney and colon mucosa. In mice, the same treatment produced dose-dependent DNA damage only in the liver. DNA repair up to 18 h appeared to be incomplete both in mice and rats. Methylazoxymethanol acetate is considered to be an active form of cycasin. While in vivo methylazoxymethanol acetate caused DNA damage, in vitro it appeared inactive and required metabolic activation, possibly consisting in its hydrolysis by esterase activity, to be able to cause DNA fragmentation.