INHIBITION BY MAGNESIUM AND CALCIUM ACETATES OF LEAD SUBACETATE-INDUCED AND NICKEL ACETATE-INDUCED LUNG-TUMORS IN STRAIN-A MICE

Abstract

The ability of the physiologically essential divalent metals Ca and Mg to inhibit the tumorigenic activities of Pb and Ni 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 per 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 Pb and Ni salts at molar doses of approximately 1, 3, 10 and 30 times the maximal tolerated dose of the tumorigen. The animals were sacrificed 30 wk after the 1st injection, and the lung tumors were counted. The Pb and Ni 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 Mg and Ca and the tumorigenic metals Ni and Pb.