LOW-LEVELS OF SERUM IONIZED MAGNESIUM ARE FOUND IN PATIENTS EARLY AFTER STROKE WHICH RESULT IN RAPID ELEVATION IN CYTOSOLIC-FREE CALCIUM AND SPASM IN CEREBRAL VASCULAR MUSCLE-CELLS

Ninety-eight patients admitted to the emergency rooms of three urban h ospitals with a diagnosis of either ischemic stroke or hemorrhagic str oke exhibited early and significant deficits in serum ionized Mg2+ (IM g2+), but not total Mg, as measured with a unique Mg2+-sensitive ion-s elective electrode. Twenty-five percent of these stroke patients exhib ited >65% reductions in the mean serum IMg2+ found in normal healthy h uman volunteers or patients admitted for minor bruises, cuts or deep l acerations. The stroke patients also demonstrated significant elevatio n in the serum ionized Ca2+ (ICa2+)/IMg2+ ratio, a sign of increased v ascular tone and cerebrovasospasm. Exposure of primary cultured canine cerebral vascular smooth muscle cells to the low concentrations of IM g2+ found in the stroke patients, e.g. 0.30-0.48 mM, resulted in rapid and marked elevations in cytosolic free calcium ions ([Ca2+](i)) as m easured with the fluorescent probe, fura-2, and digital image analysis . Coincident with the rise in [Ca2+](i), many of the cerebral vascular cells went into spasm. Reintroduction of normal extracellular Mg2+ io n concentrations failed to either lower the [Ca2+](i) overload or reve rse the rounding-up of the cerebral vascular cells. These results sugg est that changes in Mg2+ metabolism play important roles in stroke syn dromes and in the etiology of cerebrovasospasm associated with cerebra l hemorrhage. (C) 1997 Elsevier Science Ireland Ltd.