Carrier-Mediated Transport of Monocarboxylic Acids in Primary Cultured Epithelial Cells from Rabbit Oral Mucosa

Purpose. Using primary cultured rabbit oral mucosal epithelial cells (ROEpi), we investigated whether carrier-mediated drug absorption via the oral mucosal route occurs. Methods. Oral mucosal epithelial cells were isolated from rabbit buccal mucosa and cultured on tissue culture plates. When the cells reached confluence, drug uptake experiments were performed. ¹⁴C]Benzoic acid or ¹⁴C] acetic acid was used as a marker for monocarboxylic acid carrier-mediated transport. Results. The uptake of ¹⁴C]benzoic acid by ROEpi occurred at a much lower rate at 4°C than at 37°C. The metabolic inhibitors, sodium azide and 2,4-dinitrophenol, significantly inhibited the uptake of ^l4C]benzoic acid by ROEpi. Various monocarboxylic acids inhibited the uptake of ¹⁴C]benzoic acid or ¹⁴C]acetic acid by ROEpi, whereas dicarboxylic acids did not affect the uptake. Kinetic analysis using Lineweaver-Burk plots revealed that acetic acid competitively inhibited the uptake of ^l4C]benzoic acid, and benzoic acid competitively inhibited the uptake of ^l4C]acetic acid by ROEpi. Conclusions. There exists a carrier-mediated transport system for monocarboxylic acids in oral mucosal epithelial cells.