Alterations of plasma calcium and intracellular and membrane calcium in erythrocytes of patients with pre-eclampsia

Background: Changes in plasma and intracellular calcium levels have been suggested in the pathogenesis of pre-eclampsia, however, membrane calcium content has not been studied so far. We compared intracellular and membrane calcium concentrations in erythrocytes of women with pre-eclampsia, healthy pregnant woman and controls to determine a possible alteration of membrane calcium in pre-eclampsia. Subjects and methods: Eighteen untreated, healthy pregnant woman and 16 pregnant nulliparous women with manifest pre-eclampsia were included, 25 healthy, age-matched woman served as controls. Atomic absorption spectroscopy was used for measurement of intracellular and membrane calcium content in erythrocytes and plasmalemmal preparations. Results: Plasma Ca++ concentrations were significantly lower in pre-eclamptic women (1.96 +/- 0.15 mmol/l, P < 0.01, mean +/- s.e.m.) compared to healthy controls (2.43 +/- 0.14 mmol/l) or women with uncomplicated pregnancies (2.20 +/- 0.10 mmol/l). Intracellular Ca++ concentrations were not different between groups, however, membrane Ca++ content was significantly increased in the pre-eclamptic patients (1.23 +/- 0.36 mu mol/g membrane protein, P < 0.01) compared to control subjects (0.83 +/- 0.16 mu mol/g) and healthy pregnant women (0.77 +/- 0.13 mu mol/g). Conclusion: Membrane calcium content is significantly increased in pre-eclamptic women despite low plasma Ca++ concentrations. This finding suggests an altered membrane ion transport and may be of importance for the pathogenesis of pre-eclampsia.