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Human placental sulphate transport: studies on chorionic trophoblast brush border membrane vesicles.
Author(s) -
Boyd C A,
Shennan D B
Publication year - 1986
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1986.sp016173
Subject(s) - dids , chemistry , vesicle , biophysics , membrane potential , chromatography , efflux , probenecid , membrane , divalent , biochemistry , biology , pharmacology , organic chemistry
SO4(2‐) transport by microvillous brush border membrane vesicles prepared from normal‐term human placenta has been studied using an ion‐exchange column assay. The uptake of this anion is time dependent and at 20 degrees C reaches a point of equilibrium by 60 min. 4,4'‐Diisothiocyanostilbene‐2,2'‐disulphonate (DIDS) and 4‐acetamido‐4'‐isothiocyanostilbene‐2‐2'‐disulphonate (SITS) (at 10(‐4) M) were found to inhibit approximately 80% of uptake. The concentration of DIDS producing half‐maximal inhibition was approximately 10(‐5) M. In contrast furosemide and probenecid were weak inhibitors of SO4(2‐) influx. The anions Cl‐, I‐, thiocyanate (SCN‐) and gluconate (cis‐side) caused minimal inhibition of SO4(2‐) influx. Salicylate (10 mM) produced 47% inhibition. The divalent anions thiosulphate, tungstate and unlabelled SO4(2‐) (10 mM) inhibited the uptake of SO4(2‐) (at 1 mM) to the same extent as DIDS. The vesicle membrane potential was altered by varying external K+ concentration using valinomycin. The DIDS‐sensitive SO4(2‐) influx was not affected by changes in membrane potential. A novel method has been developed for studying solute efflux from pre‐loaded vesicles. Both DIDS and a reduction in temperature were effective inhibitors of SO4(2‐) efflux. These results are discussed.