The permeability of human amniotic epithelium: studies using lanthanum as a tracer.

To study the permeability of human amniotic epithelium to small molecular weight substances, pieces of nonplacental amnion, with attached chorion laeve and decidua, were exposed to solutions containing lanthanum salts and processed for electron microscopy. Lanthanum penetrated the intercellular spaces and often reached the basal lamina region. In addition, some lanthanum was bound to the glycocalyx of the microvilli on the apical surfaces of the cells. Little lanthanum was found deep to the basal lamina. The results suggest the intercellular pathway is of major importance in the movement of small molecules across amniotic epithelium.