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.
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Fong et al. (1978) studied this question.