The Effect of Various In Vitro Conditions on the Permeability Characteristics of the Buccal Mucosa

The effect of various in vitro conditions on the permeability characteristics of the buccal mucosa was assessed using caffeine (CAF) and estradiol (E(2)) as model hydrophilic and lipophilic markers, respectively. The permeation of CAF and E(2) through porcine buccal mucosa was determined in modified Ussing chambers at 37 degrees C over 4 h. Comparative permeation studies were performed through full thickness and epithelial tissues, fresh and frozen tissues, and intact and intentionally damaged tissues. Tissue integrity was monitored by the absorption of the normally impermeable fluorescein isothiocyanate (FITC)-labeled dextran 20 kDa (FD20) and tissue viability was assessed using an MTT (3-[4,5-dimethylthiazol-2-yl]-2,5-diphenyltetrazolium bromide) biochemical assay and histological evaluation. Compared to full thickness buccal tissue, permeability through the buccal epithelium was 1.8-fold greater for CAF and 16.7-fold greater for E(2). Although the fluxes of the model compounds were no different in fresh and frozen buccal epithelium, histological evaluation demonstrated signs of cellular death in frozen tissue. FD20 permeated damaged tissue, and while this was associated with an increase in CAF transport, no significant change in E(2) transport was observed. The tissue appeared to remain viable for up to 12 h postmortem using the MTT viability assay, and this was supported by histological evaluation.