K. Kisters

Plasma and membrane Ca++ and Mg++ concentrations in normal pregnancy and in preeclampsia.

OBJECTIVE Changes in intracellular Ca2+ and Mg2+ concentrations seem to be involved in the pathogenesis of preeclampsia, whereas the role of cell membranes has not been studied in detail yet. To investigate the changes in Ca2+ and Mg2+ metabolism in normal pregnancy and preeclampsia, plasma and membrane Ca2+ and Mg2+ concentrations were determined in a clinical study as compared to healthy subjects. STUDY DESIGN 25 healthy female subjects, 22 untreated healthy pregnant and 20 preeclamptic women were investigated. In each patient, plasma and membrane Ca2+ and Mg2+ content were measured. Ca2+ and Mg2+ concentrations were measured by atomic absorption spectroscopy. Erythrocyte membranes were chosen for membranous Ca2+ and Mg2+ determination. RESULTS Plasma Mg2+ concentrations were significantly lowered in the healthy pregnant group and the preeclamptic group as compared to controls (p < 0.0001). In erythrocyte membranes, Mg2+ content was found significantly decreased in the preeclamptic women as compared to healthy subjects (p < 0.001). In plasma Ca2+ concentrations there was a significant decrease in the preeclamptic group as compared to controls or healthy pregnant women (p < 0.05). Membranous Ca2+ content was significantly increased in the preeclamptic group versus controls or healthy pregnant women (p < 0.001). CONCLUSION Lowered plasma and membrane Mg2+ concentrations in preeclampsia may contribute to the development of hypertension in pregnancy. Additionally, a disturbed Ca2+ homeostasis is observed in preeclampsia.

Skeletal status after kidney transplantation by quantitative ultrasound: a 2-year follow-up study

Quantitative ultrasound (QUS) is a new and non-invasive method to assess skeletal status after kidney transplantation. We evaluated the potential use of this novel method in renal allograft recipients and studied the accuracy compared to normal controls. Thirty patients (NTP, age 47.5 ± 13.0 years) were studied 4.8 ± 3.2 years after kidney transplantation. Twenty-five healthy control persons (CON) were matched for age and sex. The left and right os calcis were studied by QUS, and speed of sound (SOS) and broadband ultrasound attenuation (BUA) were measured. Bone stiffness (BS) was calculated from these parameter and corrected for age (CBS). Differences between right and left os calcis were compared to CON to assess the side variability (mean ± SD); BS was 75 ± 25% compared to young adults, age-corrected CBS was decreased in NTP with 86 ± 25% of normal, indicating a 2-fold increased risk of fracture. SOS was 1,525 ± 47.7 m/s, BUA was 105 ± 22 dB/MHz. Mean difference between right and left os calcis was significantly higher in NTP than in CON (7.2 ± 7.1% vs. 2.1 ± 2.1%, p < 0.01). Limits of agreement of the measurements (MW of differences ± 2 SD) according to a Bland-Altmann type statistic were 16.9% and 20.7%. There was no correlation between CBS and age, cumulative steroid dose, parathyroid hormone concentrations or time after transplantation. In addition, 19 patients (49 ± 3 years, graft function: 1.8 ± 0.2 and 2.0 ± 0.2 mg%) were investigated in a 2-year follow-up study. The measures of bone stiffness at months 0 and 24 were well correlated (r < 0.9, p < 0.001), however, bone stiffness did not change significantly with time. There was a significant correlation between bone stiffness and serum calcium values (0.49, p < 0.015). Our data show altered bone structure expressed by low bone stiffness values measured by quantitative ultrasound in kidney transplant patients. However, because of relatively high interfeet variance of QUS, we suggest measurement of both os calcis to minimize measurement error after transplantation. In addition, we conclude from the data of this follow-up study that despite continued low-dose steroid treatment (< 10 mg prednisolone/day), renal transplant recipients are not subject to accelerated osteoporosis. Bone stiffness did not significantly decrease over 2 years in the present study. However, bone stiffness baseline and 2 years later were found to be decreased compared to healthy controls, a finding that is in accordance with previous data demonstrating an increased fracture rate in allograft recipients.