Comparative permeability of fresh and frozen/thawed porcine buccal mucosa towards various chemical markers.
Sometimes it is not feasible or convenient to use tissue samples immediately and they are then stored at -85 degrees C after being snap-frozen in liquid N2. Previous studies have shown that, although snap-freezing in liquid N2 does not alter the permeability properties of human buccal and vaginal mucosae towards various markers significantly, some tissue damage does occur. Slight increases in the permeability properties of the frozen/thawed human buccal mucosa towards markers were found, although these were not statistically significant. The damage does, however, not seem to affect the lipid permeability barrier to a meaningful extent. Because porcine buccal mucosa is a popular choice as a substitute for human buccal mucosa in many permeability studies, it was decided to evaluate the effect that snap-freezing, storage and thawing would have on the permeability of this mucosa when compared to human mucosae. Fresh and frozen/thawed buccal mucosa specimens were collected from freshly slaughtered pigs and permeability experiments at 20 degrees C and 1.5 ml/h, over a 24 hour time period, performed using a flow-through diffusion apparatus. The permeants tested were water, arecoline, vasopressin and 17beta-estradiol. Statistically significant differences were obtained between the flux values at steady state for water, arecoline and vasopressin through fresh and frozen/thawed porcine buccal mucosa. The estimated mean steady state flux values for 17beta-estradiol showed no statistically significant differences between the fresh appear to indicate that the lipid barrier of porcine buccal mucosa is not as resistant to snap-freezing, storage and thawing procedures as that of human mucosal tissue.