Magnesium versus lead in dietary induction of rat neoplasms

A synthetic diet with permutations of concentrations of Mg and Pb was fed to 793 postweanling male Sprague-Dawley rats. When the diet was low in content of Mg and Pb, they often developed, in the following sequence: a threefold leukocytosis; a marked reduction in cell-mediated immunocompetence; a lethal malignant lymphoma (47/71) in 8 to 24 weeks; and, finally, a lethal myelogenous leukemia (5/52) in 24 to 62 weeks. If the low-Mg diet was supplemented with excess Pb, malignant lymphoma was prevented (0/35) in 8 to 24 weeks and the usual neoplastic action of Pb was inhibited. A dietary excess of Mg alone had no epithelial neoplastic action (0/284) and little lymphoid leukemogenic action (2/84) in 8 to 62 weeks. When the diet had an excess of Mg and Pb, it favored occurrence in 41 to 62 weeks of large renal adenomas (54/92) and carcinomas (19/92) as well as thyroid adenomas (7/92) and carcinomas (4/92). If the diet high in Mg and Pb was prepared with crude rather than purified casein, leukemoid reactions with atypical lymphoid leukemia (8/102), myeloid leukemia (3/102), and cerebral gliomas (4/102) developed in 34 to 62 weeks along with renal tumors (74/102), but no thyroid tumors (0/102)more » were seen. The means by which these dietary permutations of concentrations of Mg and Pb mediate induction of some rat neoplasms is unknown. It is suggested that the effects are due to mutual displacement or other influences of these ions in activation of key enzymes involved in neoplastic transformation.« less