EVIDENCE FOR THE EXISTENCE OF A SODIUM-DEPENDENT GLUTATHIONE (GSH) TRANSPORTER - EXPRESSION OF BOVINE BRAIN CAPILLARY MESSENGER-RNA AND SIZE FRACTIONS IN XENOPUS-LAEVIS OOCYTES AND DISSOCIATION FROM GAMMA-GLUTAMYL-TRANSPEPTIDASE AND FACILITATIVE GSH TRANSPORTERS
R. Kannan et al., EVIDENCE FOR THE EXISTENCE OF A SODIUM-DEPENDENT GLUTATHIONE (GSH) TRANSPORTER - EXPRESSION OF BOVINE BRAIN CAPILLARY MESSENGER-RNA AND SIZE FRACTIONS IN XENOPUS-LAEVIS OOCYTES AND DISSOCIATION FROM GAMMA-GLUTAMYL-TRANSPEPTIDASE AND FACILITATIVE GSH TRANSPORTERS, The Journal of biological chemistry, 271(16), 1996, pp. 9754-9758
Our laboratory previously has shown apparent carrier-mediated glutathi
one (GSH) uptake across the blood-brain barrier (BBB) in two animal mo
dels, In the present study, when Xenopus oocytes were injected with bo
vine brain capillary mRNA expression of intact GSH, uptake was observe
d after 3 days, When total mRNA was converted to cDNA and subfractiona
ted with subsequent cRNA injection into oocytes, three distinct fracti
ons (5, 7-8, and 11-12) expressed carrier-mediated intact GSH transpor
t, Northern blot analysis established the presence of RcGshT, the prev
iously cloned sodium-independent hepatic canalicular transporter, only
in fraction 5, GSH transport activity in fraction 7 was significantly
inhibited by replacement of NaCl with choline chloride and by sulfobr
omophthalein-GSH, neither of which affects RcGshT, The Na+-dependent G
SH uptake kinetics exhibited high affinity (similar to 400 mu M) and l
ow affinity (similar to 10 mM) components. Fraction 11 expressed Na+-i
ndependent transport of intact GSH and also contained the GGT transcri
pt, In conclusion, we have identified three distinct sized transcripts
from bovine brain capillary mRNA which express GSH transport: one fra
ction expresses a novel Na+-dependent GSH uptake which can be dissocia
ted unequivocally from both GGT and RcGshT for the first time and whic
h may account for uptake of GSH against its electrochemical gradient a
t the BBB.