Sodium pump numbers and cation transport of lymphocytes in pregnancy-induced hypertension

Pregnancy-induced hypertension may be linked with sodium pump inhibition and an increase in vascular myocytic tone and, hence, flow impedance. All of the findings of studies on circulating plasma and blood cells are not, however, consistent with this hypothesis. We therefore assessed sodium pump numbers and cation transport in lymphocytes from 23 women with untreated pregnancy-induced hypertension, 28 normotensive pregnant women and 28 healthy non-pregnant women. We measured the maximum 3H-ouabain binding capacity to determine the sodium pump activity and the apparent dissociation constant (the reciprocal of which estimates binding affinity) by Scatchard analysis, ouabain-sensitive (pump-mediated) 86rubidium influx and ouabain-resistant (pump-independent) influx in lymphocytes in vitro. Pregnant women, whether normotensive or hypertensive, had significantly more sodium pump activity and a higher pump-mediated and pump-independent 86rubidium influx than non-pregnant women. Sodium pump activity and the pump-mediated and pump-independent 86rubidium influx all reached normal, non-pregnant levels in normotensive pregnant women 6 weeks after delivery, but remained high in women with pregnancy-induced hypertension. The normotensive and hypertensive pregnant women and non-pregnant women all had similar ouabain binding affinity. The results of our study do not support the circulating sodium pump inhibitor hypothesis in pregnancy-induced hypertension.