PERINATAL CELLULAR ION METABOLISM - P-31-NUCLEAR MAGNETIC-RESONANCE SPECTROSCOPIC ANALYSIS OF INTRACELLULAR FREE MAGNESIUM AND PH IN MATERNAL AND CORD-BLOOD ERYTHROCYTES

OBJECTIVE: We sought to establish and compare the distribution of intr acellular and extracellular magnesium and pH in cord and maternal eryt hrocytes,ter at the lime of delivery. METHODS: We used P-31-nuclear ma gnetic resonance spectroscopy and a magnesium-specific ion-selective e lectrode apparatus to evaluate plasma and intracellular red cell conte nt of free magnesium, pH, and ionized calcium in blood obtained from c ord and corresponding maternal samples. RESULTS: Cord erythrocyte intr acellular free magnesium content (110 +/- 4 mu mol/L) and pH (7.02 +/- 0.01) were lower than corresponding maternal intracellular values (14 0 +/- 9 mu mol/L, P < .05; and 7.20 +/- 0.02, P < .0005, respectively) . The extracellular cord ionized magnesium concentration in plasma was closely related to the intracellular free magnesium concentration (r = 0. 71, P < .005). Extracellular ionized magnesium and calcium were b oth greater in cord than in maternal samples (P < .05 and P < .0005, r espectively). CONCLUSION: These data indicate a differential distribut ion of extracellular and intracellular magnesium and pH in cord versus maternal blood cells. We hypothesize that these deviations are physio logical and may serve to maintain tissue oxygen delivery, while at the same time mediating the changes in vascular tone characteristic of bi rth.