DETERMINATION OF IONIZED MAGNESIUM IN PLATELETS AND CORRELATION WITH SELECTED VARIABLES

We describe a method for determining the intracellular ionized magnesi um concentration ([Mg2+](i)) in platelets by using the fluorescent pro be FURAPTRA. We determined the dissociation constant (K-D) of FURAPTRA for Mg2+ (2.26 +/- 0.29 mmol/L), within-day assay variability (CV = 6 .8%), among-day intraindividual variability (CV = 11.0%), variability after a 4-h delay in processing the blood specimen (t = 1.2, P >0.2; F = 6.2, P <0.02), and the reference interval (0.23-0.59 mmol/L) for th is assay. We also evaluated the correlation between platelet [Mg2+](i) and concentrations of selected serum electrolytes, proteins, and tota l cholesterol; age; body mass index; and gender. Only the inverse corr elation between platelet [Mg2+](i) and serum total cholesterol concent ration in men was significant (r = -0.66, P <0.005).