Sodium Transport from Blood to Brain: Inhibition by Furosemide and Amiloride

Brain sodium uptake in vivo was studied using a modified intracarotid bolus injection technique in which the uptake of 22 Na + was compared with that of the relatively impermeable molecule, [ 3 H]l-glucose. At a Na + concentration of 1.4 m M , Na + uptake was 1.74 ± 0.07 times greater than l-glucose uptake. This decreased to 1.34 ± 0.04 at 140 m M Na + , indicating saturable Na + uptake. Relative Na + extraction was not affected by pH but was inhibited by amiloride ( K i = 3 ± 10 −7 M ) and by 1 m M furosemide. The effects of these two inhibitors were additive. Brain uptake of 86 Rb + , a K + analogue, was measured to study interaction of K + with Na + transport systems. Relative 86 Rb + extraction was also inhibited by amiloride; however, it was not inhibited by furosemide. The results suggest the presence of two distinct transport systems that allow Na + to cross the luminal membrane of the brain capillary endothelial cell. These transport systems could play an important role in the movement of Na + from blood to brain.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/66216/1/j.1471-4159.1983.tb09066.x.pd