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 22Na+ was compared with that of the relatively impermeable molecule, [3H]L-glucose. At a Na+ concentration of 1.4 mM, Na+ uptake was 1.74 +/- 0.07 times greater than L-glucose uptake. This decreased to 1.34 +/- 0.04 at 140 mM Na+, indicating saturable Na+ uptake. Relative Na+ extraction was not affected by pH but was inhibited by amiloride (Ki = 3 X 10(-7) M) and by 1 mM furosemide. The effects of these two inhibitors were additive. Brain uptake of 86Rb+, a K+ analogue, was measured to study interaction of K+ with Na+ transport systems. Relative 86Rb+ 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.
D000584:Amiloride / Q000494:pharmacology*; D000818:Animals; D001693:Biological Transport, Active / Q000187:drug effects; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D005665:Furosemide / Q000494:pharmacology*; D006863:Hydrogen-Ion Concentration; D008297:Male; D011719:Pyrazines / Q000494:pharmacology*; D011868:Radioisotopes; D051381:Rats; D011919:Rats, Inbred Strains; D012413:Rubidium / Q000378:metabolism; D012964:Sodium / Q000378:metabolism*
D011719:Pyrazines; D011868:Radioisotopes; D000584:Amiloride; D005665:Furosemide; D012964:Sodium; D012413:Rubidium