Kinetic analysis of the human blood-brain barrier transport of lactate and its influence by hypercapnia.
Blood-brain barrier permeability to L-lactate was studied in 18 patients with the double indicator technique. Venous outflow curves were obtained during normo- and hypercapnia and were analyzed by means of a model that takes tracer backflux and capillary heterogeneity of transit times into account. The average unidirectional extraction of L-lactate was 15%; the transport from the blood to the brain (PS1) was 0.081 ml g-1 min-1 and the transport from the brain to the blood (PS2) was on the same order of magnitude. In hypercapnia, arterial pH decreased from 7.39 to 7.26 and PS1 to L-lactate increased significantly by 110%. PS2 also increased although a statistically significant difference compared to the resting state was not reached. It is concluded that L-lactate is easily taken up by the human brain, and that the mechanism by which it crosses the blood-brain barrier is equilibrative. Furthermore, the brain permeability to lactate is enhanced by hypercapnia and the mechanism is believed to act through the decrease in pH.
Knudsen
G M
GM
Department of Neurology, Rigshospitalet, Copenhagen, Denmark.
Paulson
O B
OB
Hertz
M M
MM
D000328:Adult; D000368:Aged; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D002463:Cell Membrane Permeability; D006801:Humans; D006935:Hypercapnia / Q000378:metabolism*; D007700:Kinetics; D007773:Lactates / Q000097:blood / Q000378:metabolism*; D019344:Lactic Acid; D008875:Middle Aged; D013499:Surface Properties
D007773:Lactates; D019344:Lactic Acid