Penetration of human vaginal and buccal mucosa by 4.4-kd and 12-kd fluorescein-isothiocyanate-labeled dextrans

Abstract

In a previous study we demonstrated that human vaginal mucosa was as permeable to water as was buccal mucosa. Water, however, is a very small molecule with a molecular weight of 18 d. To further explore similarities between these two types of mucosa with respect to permeability, it was decided to investigate the passage of two large, hydrophilic molecules across these epithelia. Specimens of fresh, clinically healthy human vaginal and buccal mucosa were taken from excised tissue obtained during vaginal hysterectomies and various oral surgical procedures. Seven biopsy materials from each specimen were mounted in flow-through diffusion cells (exposed area, 0.039 cm 2), and their permeability to 4.4- and 12-kd fluorescein-isothiocyanate-labeled dextrans was determined through use of a continuous flow-through perfusion system. Dextran was detected by means of a fluo-rospectrophotometric method at excitation and emission wave lengths of 498 and 520 nm, respectively. Specimens were examined histologically before and after permeability experiments, and similarities between vaginal and buccal tissues were verified. No statistically significant differences between the flux values of the 4.4-kd dextran across vaginal and buccal mucosa were found. However, for the 12-kd dextran the flux rate across buccal mucosa was significantly higher than the rate across vaginal mucosa. These results demonstrate that human vaginal mucosa is for practical purposes as permeable as buccal mucosa to 4.4-kd hydrophilic molecules. This further supports the hypothesis that vaginal mucosa may be a useful model for studying the passage across buccal mucosa of chemical compounds and therapeutic agents that are less than approximately 4.4 kd in molecular mass. For a 12-kd dextran the flux rate across buccal mucosa is significantly higher than the flux rate across vaginal mucosa, and the model becomes inaccurate.