A CROSS-SECTIONAL STUDY OF BASAL PLATELET INTRACELLULAR FREE CALCIUM-CONCENTRATION IN NORMOTENSIVE AND HYPERTENSIVE PRIMIGRAVID PREGNANCIES

The intracellular free calcium concentration ([Ca2+](i)) in washed human platelets was measured using the fluorescent indicator, fura-2, in a cross-sectional study of 36 normotensive, primigravid volunteers, 12 in each trimester of pregnancy and a further 12 at 6 weeks post partum. The results were compared with those obtained from 30 normal female volunteers not using oral contraception. The mean basal [Ca2+](i) in the platelets of the pregnant women in the first two trimesters (115.6 ± 6.7 and 120.1 ± 5.7 nmol/l, respectively) was not shown to differ significantly from that of normal non-pregnant volunteers (112.3 ± 2.9 nmol/l). However, during the third trimester a significant increase in [Ca2+](i) was noted (134.0 ± 4.9 nmol/l; P < 0.05), with a return to normal values in the post-partum period (108.2 ± 6.1 nmol/l). [Ca2+](i) was also measured in the platelets of a group of 12 primigravid pregnant women in the third trimester whose pregnancies were complicated by gestational hypertension (pregnancy-induced hypertension and preeclampsia). A significant rise in basal [Ca2+](i) was noted in the platelets of primigravidae whose pregnancies were complicated by pre-eclampsia (163.6 ± 8.8 nmol/l) as compared with normotensive, third-trimester primigravidae (P < 0.02). However, no correlation could be demonstrated between [Ca2+](i) and systemic blood pressure.