INVITRO PENETRATION OF TRITIUM-LABELED WATER (THO) AND [H-3] PBTX-3 (A RED TIDE TOXIN) THROUGH MONKEY BUCCAL MUCOSA AND SKIN

The permeability coefficients (K(p)) for tritium-labelled water (THO) were determined in human and monkey skin, and monkey buccal mucosa. K(p) of human skin (0.47 x 10(-3) cm/h) correlated favorably with previous reports. K(p) of hydrated monkey skin for THO (0.77 x 10(-3) cm/h) was not significantly different (P > 0.05) from K(p) of hydrate human skin (0.88 x 10(-3) cm/h). K(p) of monkey buccal mucosa for THO (6.15 x 10(-3) cm/h) was significantly greater than that for monkey skin. Penetration and disposition of [H-3]PbTx-3 into layers of monkey buccal mucosa and skin was determined. [H-3]PbTx-3 (5-7-mu-Ci) dissolved in 2 ml of water was applied to epithelial/epidermal surface (2.8 cm2) at zero time. The relative percent dose recovered from the upper layers of buccal mucosa (epithelium) and skin (epidermis) varied, but at each time interval was less than 2.5% of the dose. At most of the time intervals (2-24 h), a larger percent of the dose was recovered from the inner layer of the buccal mucosa (lamina propria) than from the inner layer of skin (dermis). After 24 h, as much as 34 or 13% of the dose was recovered from lamina propria or dermis, respectively. At each time interval studied, less than 2% of dose of [H-3]PbTx-3 penetrated into the receptor fluid which bathed the inner surfaces of the lamina propria or dermis. The results of this study demonstrate that monkey buccal mucosa is more permeable than skin to THO and PbTx-3.