In vitro transmucosal permeation of (14C)-dibutyl phthalate [(I4C)DBP], across intact mucosal hamster tissue compared to keratin-stripped mucosal tissue indicated no significant difference ( p 2 0.069) in (14C)-DBโฌ? However, significantly greater ( p < 0.022) DBP was found to be concentrated in the keratin-stripped tissue after a period of 6 h. The amount of (I4C)-DBP permeating botb tissues followed a similar linear increase for = 3 h. However, between 3 and 4 h, the rate of permeation through the untraumatized tissue significantly decreased. This was followed by a rapid linear increase for the next 3 h. In contrast, the cumulative amount of (14C)-DBP permeating the traumatized tissue showed a linear correlation (r = 0.995) over the 6-h period. A theoretical two-layer model was constructed to allow computer simulations of the (14C)-DBP permeation. It was indicated that an average diffusion coefficient for a single DBP molecule through the intact keratin layer would be = 100 times less than through the remaining layer of the model. The model has enabled a possible explanation to be put forward, describing the role of the keratin layer in the permeation of plasticizer through mucosal tissue.
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