Functional differentiation of enterocytes in the follicle-associated epithelium of rat Peyer's patch.

The ability of the follicle-associated epithelium (FAE) of rat Peyer's patch to accumulate valine has been measured using a new technique of autoradiographic analysis. Maximum uptake of valine was achieved by enterocytes present in the dome region of the FAE. Valine uptake was not seen in enterocytes present on the lower slopes of the FAE or in follicle-associated crypts. The ability of the FAE to absorb valine was generally much less than that seen in enterocytes present on adjacent villi. The main reason for this discrepancy lay in the apparent inability of the FAE to develop a second phase of amino acid transport similar to that seen in villus enterocytes. It is suggested that this failure results from some unexplained interaction taking place between the FAE and its underlying lymphoid tissue.