Caracterización del canal epitelial de sodio en sinciciotrofoblasto de placenta humana preeclamptica

the syncytiotrophoblast (sct), a multinucleated epithelium forming the outer layer of chorionic villi, acts in human placenta as a transporting barrier regulating the transference of nutrients, solutes and water between maternal and fetal blood. electrolyte homeostasis and extracellular fluid volume are maintained primarily by regulated na+ transport. the present study was conducted to analyze the presence of the epithelial na channel (enac) in placental tissue from normal and pre-eclamptic women and in bewo cell, a model of a human sct. changes in the expression of these proteins during sodium transport across the placenta may be related to the pathogeny of pre-eclampsia. the role that enac and na+ transport deregulation play on human placental tissues still remains unknown although in aldosterone-responsive epithelial cells (kidney, colon), abnormalities upregulating its activity lead to increased na+ uptake and hypertension (i.e. liddle′s syndrome) whereas a diminished channel activity can result in the pseudohypoaldosteronisn syndrome with salt loss and hypotension. our results show that enac is expressed in the apical membrane of normal syncytiotrophoblast. the amplified fragment of a-enac was cloned and sequenced having a 100% identity with the sequence of a-enac obtained from genbanktm (scnn1a, accession number z92981). we found that the transcription of the a-enac mrna was not detectable in preeclamptic placentas and the protein was not observed with immunohistochemistry staining, probably indicating a low protein expression level. in bewo cells enac was found and its expression is regulated by aldosterone, vasopressin, progesterone and estradiol. with patch clamp techniques we studied the currents trough enac channels in bewo cells. we observed currents that were blocked by 10 μm amiloride in cells incubated in 100 nm aldosterone for 12 hs. the amplitude of this current was 20-fold the basal current, a reversal potential of 3 mv and a conductance of 127 ± 2