The ability of the physiologically essential divalent metals
calcium and
magnesium to inhibit the tumorigenic activities of lead and
nickel towards the lungs of strain A mice was investigated. The tumorigenic
salts lead(II) subacetate and
nickel(II) acetate were injected i.p. at their maximal tolerated doses (0.04 mmol/kg/injection of each
metal) for a total of 24
injections, whenever possible.
Calcium(II)
acetate and
magnesium(II)
acetate were administered in the same preparation along with the lead and
nickel salts at molar doses of approximately 1, 3, 10, and 30 times the maximal tolerated dose of the tumorigen. The animals were sacrificed 30 weeks after the first injection, and the lung
tumors were counted. The lead and
nickel salts, administered alone, each produced a significant increase in the observed number of lung
adenomas per mouse. When administered with any of the doses of
calcium acetate or
magnesium acetate tested, neither
lead subacetate nor
nickel acetate showed any significant tumorigenic activity.
Calcium acetate alone (total dose, 11 mmol/kg of
body weight) appeared to yield a significant rise in lung
adenomas observed. The results indicate an antagonism between
magnesium and
calcium and the tumorigenic metals
nickel and lead.