STIMULATING EFFECT - OF EXCESS IRON FEEDING ON SPONTANEOUS LUNG-TUMORPROMOTION IN MICE

This study was undertaken to estimate if dietary iron could stimulate factors which promote spontaneous lung tumorigenesis in A/J mice, by m easuring biochemical parameters of oxidative stress on pulmonary nucle i, ornithine decarboxylase (ODC) and spermidine/spermine N-1-acetyltra nsferase (SAT) activities as markers of tumor promotion. Feeding exces sive iron (500%) to A/J mice for 28 weeks significantly elevated pulmo nary DNA single strand break (DNA-SSB) as well as nuclear thiobarbitur ic acid reactive substances (TEARS) in connection with the increase of nuclear nonheme iron level. In contrast, nuclear alpha-tocopherol lev els in the iron-loaded group significantly decreased as compared to th at in the control group. Pulmonary ODC and SAT activities showed incre asing tendency on feeding excess iron for 28 week. These results sugge st that dietary iron stimulates spontaneous lung tumor promotion in A/ J mim, partly due to the enhancement of oxidative damage to the pulmon ary nuclei.