Loss of dopamine D1-like receptors in the umbilical artery of pre-eclamptic subjects.

1. The influence of pre-eclampsia on the density and pattern of dopamine D1-like receptors was studied in frozen samples of the placental end of the umbilical artery by using radioligand binding and autoradiographic techniques in combination. 2. Analysis was performed on normotensive (n = 10) and pre-eclamptic subjects (n = 9) undergoing caesarean delivery, using [3H]-SCH 23390 as a ligand. Pre-eclamptic patients received a low salt diet and were treated with magnesium sulphate and hydralazine. The possibility that this treatment may cause changes in the density of dopamine D1-like receptors was evaluated by treating male Wistar rats in the same way and by determining [3H]-SCH 23390 binding in sections of the kidney which represents an organ containing dopamine D1-like receptors. 3. The density of dopamine D1-like receptors of the umbilical artery, which are probably vasodilatory, was decreased in pre-eclamptic compared with normotensive subjects. In contrast, the affinity of the radioligand for dopamine D1-like receptors was not statistically different between normotensive and pre-eclamptic subjects. Low salt diet, magnesium sulphate and hydralazine treatment did not affect [3H]-SCH 23390 binding to sections of rat kidney. This suggests that changes in the density of dopamine D1-like receptors in pre-eclamptic patients are a specific phenomenon not dependent upon antihypertensive measures. 4. Analysis of the pharmacological profile of [3H]-SCH 23390 binding to sections of the umbilical artery both in normotensive and pre-eclamptic subjects indicates the labelling of dopamine D5 receptors. 5. These findings collectively suggest that the dopaminergic vasodilatory tone in the umbilical artery is impaired in pre-eclampsia. The possible significance of these data should be clarified in future studies.