The permeability of rat palatal mucosa maintained in organ culture.

The intercellular permeability barrier of neonatal rat palatal mucosa maintained in organ culture for periods up to 24 days was studied ultrastructurally using the tracers horseradish peroxidase and lanthanum nitrate. At all time intervals examined the limit of penetration of the tracers corresponded to the level at which the membrane-coating granules were being discharged. However, in the cultured mucosa, extrusion of granules occurred closer to the granular cell-keratin junction after 6 and 12 days in vitro than at other time intervals. This probably is a reflexion of the higher rate of tissue turnover at these times. It is concluded that a permeability barrier comparable with that described in vivo is produced by the epithelium during maintenance inorgan culture and is further evidence of the functional integrity of the tissue in vitro.