MUSCARINIC CHOLINERGIC RECEPTORS AND ACETYLCHOLINESTERASE ACTIVITY INUMBILICAL ARTERY AND VEIN IN PREGNANCY-INDUCED HYPERTENSION (PREECLAMPSIA)

The influence of pregnancy-induced hypertension (pre-eclampsia) on mus carinic cholinergic receptors and on acetylcholinesterase (AChE) activ ity was investigated using frozen sections of the umbilical artery and vein. Pre-eclamptic patients undergoing Caesarean delivery and normot ensive pregnant control woman undergoing Caesarean delivery with simil ar parity, gestation length and age were examined. Muscarinic choliner gic receptors were assayed in frozen sections of the umbilical artery and vein by a radioligand binding assay technique, using [H-3]-N-methy l scopolamine (NMS) as a ligand. AChE was demonstrated with a histoche mical technique associated with microdensitometry. [H-3]-NMS was speci fically bound to sections of both umbilical artery and vein in a manne r consistent with the labelling of muscarinic cholinergic receptors. T he affinity of the radioligand was similar in the two vessels, whereas the maximum density of binding sites (B-max) was higher in the umbili cal vein than in the artery. A faint AChE reactivity was observed in t he tunica media of both umbilical artery and vein. In pre-eclampsia, a loss of [H-3]-NMS binding sites not accompanied by changes in the aff inity of radioligand was found. The decrease of muscarinic cholinergic receptors involved to a greater extent the umbilical artery than the vein. No differences in ACHE activity were found at the level of umbil ical artery and vein between control and pre-eclamptic subjects. These , findings suggest that pre-eclampsia is characterized by sc loss of m uscarinic cholinergic receptors in the umbilical circulation not accom panied by changes of the acetylcholine catabolizing enzyme AChE. It is possible that the decreased density of vascular muscarinic cholinergi c receptors in pregnancy-induced hypertension contribute to the increa sed resistance of the umbilical circulation occurring in pre-eclampsia .