STUDIES OF INTESTINAL ABSORPTION AND SECRETION .3. SIGNIFICANCE OF INTERCELLULAR SPACES FOR NET FLUXES OF FLUID IN SMALL INTESTINUM (EXPERIMENTS IN RATS)

With a specially devised in vivo perfusion technique sections of the upper jejunum of conscious rats are perfused extracorporally with water, isotonic (0.9%) and hypertonic (1.8%) solutions of saline. The net fluxes of volume are measured. Then the same section of gut is perfused with osmium tetroxide (1%), fixed and studied by electron microscopy. In case of a net volume flux - directed either towards the blood or towards the lumen - the intercellular spaces of the mucosal layer are markedly dilated. Under isotonic conditions the intercellular spaces appear unchanged. Under net volume absorption the dilatation begins in the luminal part of the mucosal layer, whereas net volume secretion is accompanied by dilatation in the basal parts of the intercellular spaces. The contact between neighbouring mucosal cells at the tight junctions" and "interdigitations" remains intact under all of the above conditions. The morphologic changes seem to indicate that the intercellular spaces play an important role as a pathway for the fluid transport across the intestinal mucosa in both directions. © 1969 Springer-Verlag."