HETEROGENOUS NA-ATPASE EXPRESSION IN THE EPITHELIA OF RABBIT GUT-ASSOCIATED LYMPHOID-TISSUES(, K+)

Na+, K+-ATPase expression in the epithelia of rabbit gut-associated ly mphoid tissue was measured using indirect immunofluorescence and confo cal laser scanning microscopy. All four major sites of aggregated lymp hoid tissue, i.e. Peyer's patch, sacculus rotundus, caecal patch and a ppendix, were studied. Na+, K+-ATPase expression was localized to the basolateral surface of cells of the follicle-associated epithelium (FA E) and adjacent villous or surface epithelia (non-FAE), where increase d expression during enterocyte migration was evident. In the FAE, expr ession of Na+, K+-ATPase appeared to be lower in the specialized M cel ls than in enterocytic-type cells, although expression in both cell ty pes was lower than in adjacent non-FAE. Quantification of immunofluore scent staining of Na+, K+-ATPase by confocal laser scanning imaging sh owed a reduction of expression in the FAE to approximately 20-60% rela tive to that in the adjacent non-FAE. These results are consistent wit h a primary role of the FAE in mucosal immunity with minimal involveme nt in active solute absorption.