Permeability of vaginal mucosa to water at normal and elevated temperatures

A number of studies have clearly demonstrated that human vaginal mucosa may be used as a model of buccal mucosa for a variety of in vitro permeability studies on drugs and other chemical compounds. Furthermore, at between 25 degrees and 37 degrees C, a linear temperature-dependence of water flux across this mucosa, which was attributed to an increased fluidity of the principal lipoidal permeability barrier, was found to exist. The objective of the present study was to examine the behaviour of the above barrier on water fluxes at normal and elevated temperatures. Clinically healthy human vaginal mucosa specimens were obtained from excess tissue removed during a vaginal hysterectomy from a single patient, snap-frozen in liquid nitrogen and stored for 6 months at -85 degrees C. Seven sections from the mucosa were thawed in phosphate-buffered saline (PBS) and mounted in flow-through diffusion cells (exposed area 0.039 cm2). Their permeability to tritiated water was determined using a continuous flow-through perfusion system at temperatures of 37 degrees, 39 degrees and 41 degrees C. Three permeability experiments were performed at each temperature setting. Specimens were subjected to histological examination before and after permeability experiments. Mean water flux rates at steady state (10-24 h) were found to be 2,356 +/- 71 SEM, 3,020 +/- 38 SEM and 3,659 +/- 116 SEM cpm. cm-2.min-1, at temperatures of 37 degrees, 39 degrees and 41 degrees C, respectively. A linear regression analysis and plot (r2 = 0.99) displayed a slope of 325 +/- 4 SEM cpm.cm-2.min-1/degree C. The results of this study showed that, notwithstanding cellular damage, the principal physical permeability barrier was linearly temperature-dependent between the temperatures studied, providing further support for the concept that this barrier is lipoidal in nature.