PLENARY SESSION II, SATURDAY
Microcirculatory disorders of diabetes mellitus (DM)—a disease that when controlled was early identified with Mg loss—have characteristics in common with those of experimental Mg deficiency. Low blood Mg (in concert with high Ca) increases platelet aggregability and blood coagulation—which have been implicated in the pathogenesis of DM, myocardial infarction (MI) and eclampsia. Low serum Mg, though present at phases of the disorders in many cases, is an unreliable index of Mg deficiency. Low ionized Mg in erythrocytes (determined by utilizing nonmagnetic resonance) is present in all, as well as in hypertension (HT) unrelated to DM or toxemias of pregnancy. Using a new ion-selective electrode specific for the Mg ion, we have found that low levels of the biologically active ionized Mg is present in whole blood, as well as in plasma and serum, of patients with HT, with or without DM, of patients scheduled for open-heart surgery, and of preeclamptic patients. Recent studies by others have shown that there is also endothelial damage in DM, and in cardiac and preeclamptic patients. Low Mg concentration influences endothelial integrity and its production of prostacyclin (PGI)—the vasodilating, antiaggregating prostanoid, mediating its activity, and increases release of thromboxane (TXA)—the vasoconstricting platelet aggregating prostanoid. Other endothelial derivatives (endothelium-derived relaxing factor [EDRF], endothelin, and fibronectin may also be affected by Mg. Low Mg favors a high TXA/PGI ratio. It is suggested that imbalance of the prostanoids, and that of the other endothelial derivatives may be linked to the low Mg reported in these diseases. With the new Mg ion-selective electrode, which uses a neutral carrier-based membrane to provide readings in 60-90 seconds, it will be possible to resolve the problem of laboratory diagnosis of Mg deficiency. With growing recognition of the roles of the endothelial factors, this should improve understanding of the vulnerability of diabetics to HT and other vasospastic and structural arterial diseases, and to cardiomyopathy and MI and other thromboembolic conditions, as well as to preeclampsia.
J Am Coll Nutr 11:608 (1992)
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