Serum and erythrocyte magnesium concentrations in solid tumours: relationship with stage of malignancy.

Magnesaemia is often decreased in solid tumours, but magnesium (Mg) is mainly an intracellular cation and serum levels do not reflect actual body stores. In this study serum Mg (SMg) and erythrocyte Mg (EMg) concentrations were measured in 40 healthy controls and in 108 patients affected by various types of tumour (50 lung cancers, 25 breast cancers, 18 ovarian cancers, and 15 oropharyngeal and hypopharyngeal cancers). EMg was higher (P < 0.05) and SMg lower P < 0.001) in neoplastic patients than in controls. All tumour types behaved in the same way, though in the lung cancer group the increase in EMg did not reach statistical significance in comparison with the control group (P = 0.05). The extent to which EMg was increased and SMg decreased was positively correlated with the advancement in the stage of malignancy. These results suggest that in neoplastic disease Mg requirement is not only increased in tumour tissue, but also in erythrocytes. The increase in EMg may derive from a change in the red blood cell membrane, facilitating intracellular concentration of magnesium for transport to the tumour. The concomitant decrease in SMg may be the consequence of the enhanced erythrocyte uptake of magnesium from the extracellular circulating pool.

Serum and erythrocyte levels of magnesium in microcytosis: comparison between heterozygous beta-thalassemia and sideropenic anemia.

In thalassemia erythrocyte cation permeability is increased, but the increment in ATPase-dependent cation pumps maintains normal concentrations of Ca++, Na+ and K+. In this study we investigated erythrocyte concentrations of Mg++ in heterozygous beta-thalassemia and in microcytic sideropenic anemia. Twenty-five healthy controls, 40 heterozygous beta-thalassemics and 25 patients with sideropenic anemia were studied. Erythrocyte Mg++ was assayed either by atomic absorption or by standard laboratory methods. Erythrocyte Mg++ was significantly lower in the beta-thalassemia group than in the other two groups (p less than 0.001). Serum magnesium was significantly lower in sideropenic anemia patients than in beta-thalassemics and in controls (p less than 0.01), whereas these latter two groups showed similar values. Our results suggest that the increment in ATPase-dependent cation pumps is not sufficient to maintain normal erythrocyte Mg++ concentrations in heterozygous beta-thalassemia. In sideropenic anemia cation permeability is not increased, therefore erythrocyte Mg++ is normal. Low serum Mg++ levels in sideropenic anemia could be explained by a primary Mg++ deficit associated with sideropenia.

Changes in serum, erythrocyte, and urinary magnesium after a single dose of cisplatin combination chemotherapy.

The changes in serum and erythrocyte Mg concentrations and in renal Mg excretion induced by a single dose of cisplatin (100 mg/mq body surface area) were investigated in 16 patients with lung cancer. Magnesuria increased significantly (P less than 0.001) the day after cisplatin administration, returned to basal levels in the following days, and increased again on the 7th day (P less than 0.05). Magnesaemia decreased gradually and after 7 was significantly lower than before treatment (P less than 0.05). Erythrocyte Mg decreased significantly on days 1 (P less than 0.05) and 2 (P less than 0.001) after cisplatin administration, began to increase on day 4, and recovered to pretreatment values on day 7. These results suggest that, besides the well known damage to tubular function with consequent increase in renal Mg wasting, cisplatin may also interfere with Mg metabolism at cellular and subcellular levels. The activity of the drug on nucleic acids and membrane transport systems, where Mg is abundant and exerts important stabilizing functions, could induce Mg mobilization and increased membrane permeability, with a consequent shift of Mg from cells into the blood stream. This would counterbalance the increase in magnesuria, and magnesaemia would decrease significantly only when intracellular Mg returns to pretreatment levels.