The Maxi-Chloride Channel in Human Syncytiotrophoblast: A Pathway for Taurine Efflux in Placental Volume RegulationReportar como inadecuado




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Resumen

Taurine Tau, the most abundant amino acid in fetal blood, is highly concentrated in human placenta. During pregnancy, Tau is involved inthe neurological development of the fetus, and in volume regulation of the placenta. The placenta may release taurine in parallel with Kþand Cl in response to an increase in cell volume. However, the pathway for the volume-activated taurine efflux is unknown. One candidateis a voltage-dependent Maxi-chloride channel from apical syncytiotrophoblast membrane MVM, with a conductance over 200 pS and multiplesubconductance states. Our aim was to study whether this channel could be a Tau conductive pathway in the MVM. Purified human placentalMVM were reconstituted into giant liposomes suitable for patch clamp recordings. Typical Maxi-chloride channel activity was detected in symmetricalchloride Cl solutions, and then taurine Tau, Aspartate Asp, and glutamate Glu solutions were used in the bath of excised patchesto detect single channel currents carried by these anions. The relative permeabilities P, estimated from the shift in reversal potential of currentvoltagecurves after anion replacement, were as follows: Chloride > Taurine ¼ Glutamate ¼ Aspartate. In Tau symmetric conditions usingequivalent Cl concentrations, the slope conductance was 62.4 7.3 pS. The data shows that Tau and other amino acids diffuse through theMaxi-chloride channel, which could be of great importance as part of the mechanism involved in the volume regulation process in humanplacenta.



Autor: Vallejos, C.; - Riquelme Pino, Gloria; -

Fuente: http://repositorio.uchile.cl/



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