A cross-sectional study of basal platelet intracellular free calcium concentration in normotensive and hypertensive primigravid pregnancies

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Abstract
1. 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. 2. 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; P < 0.05), with a return to normal values in the post-partum period (108.2 .+-. 6.1 nmol/l). 3. [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 preclampsia). 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.