Morpho-functional modifications of human syncytiotrophoblast plasma membrane during Pregnancy Induced Hypertension

Abstract

A decrease of Na+/K(+)-ATPase activity has been reported in syncytiotrophoblast plasma membrane (SPM) obtained from pregnancy induced hypertensive (PIH) women. The aim of the present work was to verify if the reported modifications in activity are due to a decreased number of enzymatic molecules or to a conformational change of the enzyme itself. Morphological studies were performed in order to better understand the relations between the enzymatic protein and the lipid bilayer. Kinetic studies were also performed. SPM obtained from PIH showed: i) an increased affinity of Na+/K(+)-ATPase for ouabain binding, ii) a significant change in the maximum velocity of the enzyme, iii) a higher distribution factor (DF) of intramembrane particles (IMPs) in the exoplasmic face of the membrane, iv) a decreased mean diameter of IMPs both in the protoplasmic and exoplasmic faces, v) a decreased number of IMPs in the exoplasmic face. In conclusion, a conformational modification seems to be at the basis of the decreased Na+/K(+)-ATPase activity during PIH as suggested by binding, ultrastructural and kinetic data herein reported.

Gestational hypertension plasma and human umbilical vein endothelial cells: an in vitro study

“…The inhibition of Na , K -ATPase activity of HUVEC plasma membrane caused by GH plasma is consistent with our previous data reporting decreased enzymatic activity in different cellular types during GH [28]. Nitric oxide has recently been identi®ed as a relevant factor in the regulation of Na , K -ATPase activity in rabbit aorta, playing a role in its activation by agonists [10].…”