In-vitro evidence for carrier-mediated uptake of acidic drugs by isolated bovine brain capillaries.

[3H]Acetic acid was taken up into the isolated brain capillaries in a temperature and concentration dependent manner. The initial uptake rates were pH dependent over the range 5.0-7.4. An increase of the uptake rate with decrease in medium pH was not seen in the presence of unlabelled acetic acid (10 mM). The uptake of [3H]acetic acid was significantly reduced in the presence of several drugs having a monocarboxylic group. The initial uptake of [14C]salicylic acid was also pH dependent and was inhibited by acetic acid and acidic drugs. A mutually competitive inhibition was observed for the uptake of acetic acid and salicylic acid. The present study demonstrates that acidic drugs having a monocarboxylic group are transported by a common carrier-mediated system into the brain capillaries.