Enhancing effect of high dietary iron on lung tumorigenesis in mice.

In our previous reports we indicated that oxidative stress on pulmonary nuclei caused by oxy radicals could be involved in glycerol-enhanced lung tumorigenesis in ddY mice treated with 4-nitroquinoline 1-oxide (4NQO). This study was undertaken to estimate if dietary iron could act as a stimulating factor on lung tumorigenesis in mice treated with 4NQO plus glycerol. Feeding excessive iron to mice treated with these agents significantly increased nuclear thiobarbituric acid reactive substances (TBARS) and DNA single strand breaks (DNA-SSB) in the lungs as compared with mice fed adequate iron 4 weeks after 4NQO injection. Nuclear non-haem iron level in mice fed excessive iron was also higher than the level in mice fed adequate iron. Twenty-three weeks after 4NQO injection (at the end of this experiment) the supply of excessive iron for 4 and 23 weeks after 4NQO injection stimulated the development of lung tumors in mice treated with 4NQO plus glycerol. These results suggest that a high dietary iron level acts as a stimulating factor on lung tumorigenesis in mice treated with 4NQO plus glycerol.