Continuity of electron histochemically demonstrable substances in the basal lamina, the ground substance of the connective tissue and the intercellular spaces of eptihelial cells of rat gingiva.

Rat gingiva was examined in the electron microscope for substances reactive to ruthenium red and lanthanum nitrate. Both reagents produced an electron-dense band in the basal lamina where the lamina lucida could not be distinguished from the lamina densa. There was continuity between this electron-dense material and that in the ground substance of the adjacent connective tissue and the intercellular spaces of the adjacent epithelial cells. It was concluded that the lamina lucida is not a simple fluid space but is occupied by histchemically demonstrable substances, probably proteoglycans, and that there is a continuum of histochemically demonstrable proteoglycan through which metabolites pass between the blood vessels of the connective tissue and the epithelial cells.