pH dependence of blood-brain barrier permeability to lactate and nicotine.
Brain uptake of radiolabeled D and L-lactate, D-glucose and nicotine, as measured by the intra-carotid bolus method, was examined over a range of pH of the injected solution. The uptake of L-lactate was highest at pH 6.1, and lowered significantly at pH 7.2, 7.5 and 8.4. In contrast, the uptake of the D-enantiomer was not as dramatically affected. Glucose uptake was not affected by alterations in pH. Nicotine uptake decreased with pH reduction through a range of 8.3-4.2. These data suggest that it is the uncharged molecule which penetrates the blood-brain barrier by both carrier and lipid mediation. A mechanism relating to these observations is postulated and possible relevance to lactate washout from ischemic brain discussed.
D000818:Animals; D001812:Blood-Brain Barrier; D001921:Brain / Q000378:metabolism*; D005260:Female; D005947:Glucose / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D007773:Lactates / Q000378:metabolism*; D008297:Male; D008833:Microcirculation; D009538:Nicotine / Q000378:metabolism*; D051381:Rats
D007773:Lactates; D009538:Nicotine; D005947:Glucose