Zinc deficiency and methylbenzylnitrosamine-induced esophageal cancer in rats

Dietary zinc deficiency increases the incidence of and shortens the lag time for induction of esophageal tumors in rats by methylbenzylnitrosamine (MBN). Groups of control and zinc-deficient outbred Charles River CD rats were given 24, 17, 8, or 4 doses of MBN, administered twice weekly by intragastric intubation at doses of 2 mg/kg body weight. Between 58 and 93 days after the beginning of treatment, all rats were killed and examined. The frequency of esophageal tumors in the zinc-deficient groups was significantly higher than in the corresponding control groups. Following ip injection of [methyl-14C]MBN, DNA and RNA of esophagus and liver were more noticeably labeled than kidney, lung, and small intestine, which exhibited only modest labeling. In vitro incubation with [14C]MBN of tissue slices from esophagus, liver, kidney, and small intestine produced similar results. This pattern correlates well with the results of our studies of MBN-induced esophageal tumorigenesis.