M. Homma et al., High-affinity efflux transport system for glutathione conjugates on the luminal membrane of a mouse brain capillary endothelial cell line (MBEC4), J PHARM EXP, 288(1), 1999, pp. 198-203
Citations number
33
Categorie Soggetti
Pharmacology & Toxicology
Journal title
JOURNAL OF PHARMACOLOGY AND EXPERIMENTAL THERAPEUTICS
Cumulative evidence suggests that several organic anions are excreted from
the brain to the blood across the blood-brain barrier. in the present study
, we carried out a kinetic investigation of the transport activity in MBEC4
, an immortalized cell line established from BALB/c mouse cerebral microves
sel endothelial cells. The presence of an efflux system in intact cells was
examined by using monochlorobimane (MCB), which is conjugated with glutath
ione intracellularly to produce glutathione bimane (GS-B). The efflux of GS
-B was inhibited by ATP depletion and also by 1-chloro-2,4-dinitrobenzne, a
precursor of 2,4-dinitrophenyl-S-glutathione, in a concentration-dependent
manner. Using this MBEC4 monolayer, we investigated the direction of this
transport activity. Although the efflux of GS-B was observed on both lumina
l and abluminal sides of MBEC4 monolayer, the profile differed for the two
sides with respect to the concentration dependence of MCB; the analysis sug
gested the presence of high-affinity transport system on the luminal side.
To investigate the mechanism for the transport, we examined the ATP-depende
nt uptake of GS-B into the membrane vesicles prepared from MBEC4. ATP-depen
dent uptake systems with high (K-m = 35 nM) and low (K-m = 14 mu M) affinit
ies were identified. These results suggested that this high-affinity transp
ort system of glutathione conjugates is expressed on the luminal side of th
e blood-brain barrier and is involved in the detoxification of xenobiotics.