PENETRATION OF HUMAN VAGINAL AND BUCCAL MUCOSA BY 4.4-KD AND 12-KD FLUORESCEIN-ISOTHIOCYANATE-LABELED DEXTRANS

In a previous study we demonstrated that human vaginal mucosa was as p ermeable to water as was buccal mucosa. Water, however, is a very smal l molecule with a molecular weight of 18 d. To further explore similar ities between these two types of mucosa with respect to permeability, it was decided to investigate the passage of two large, hydrophilic mo lecules across these epithelia. Specimens of fresh, clinically healthy human vaginal and buccal mucosa were taken from excised tissue obtain ed during vaginal hysterectomies and various oral surgical procedures. Seven biopsy materials from each specimen were mounted in flow-throug h diffusion cells (exposed area, 0.039 cm(2)), and their permeability to 3.4- and 12-kd fluorescein-isothiocyanate-labeled dextrans was dete rmined through use of a continuous flow-through perfusion system. Dext ran was detected by means of a fluorospectrophotometric method at exci tation and emission wave lengths of 498 and 520 nm, respectively. Spec imens were examined histologically before and after permeability exper iments, and similarities between vaginal and buccal tissues were verif ied. No statistically significant differences between the flux values of the 4.4-kd dextran across vaginal and buccal mucosa were found. How ever, for the 12-kd dextran the flux rate across buccal mucosa was sig nificantly higher than the rate across vaginal mucosa. These results d emonstrate that human vaginal mucosa is for practical purposes as perm eable as buccal mucosa to 4.4-kd hydrophilic molecules. This further s upports the hypothesis that vaginal mucosa may be a useful model for s tudying the passage across buccal mucosa of chemical compounds and the rapeutic agents that are less than approximately 4.4 kd in molecular m ass. For a 12-kd dextran the flux rate across buccal mucosa is signifi cantly higher than the flux rate across vaginal mucosa, and the model becomes inaccurate.