DIPEPTIDYL PEPTIDASE IV EXPRESSION IN RAT JEJUNAL CRYPT-VILLUS AXIS IS CONTROLLED AT MESSENGER-RNA LEVEL

The expression of dipeptidyl peptidase IV (DPP IV), an intestinal brush-border hydrolase, has been studied in the rat jejunum crypt-villus axis. DPP IV enzyme activity is lower in crypt cells than in villus cells. Indirect immunofluorescence studies, using a polyclonal antibody raised against purified DPP IV, show a gradient of immunoreactivity from the crypts to the villi that was quantified using confocal laser scanning microscopy. Accordingly, Western blot analysis demonstrates that the steady-state amount of DPP IV is much lower in crypt cells than in villus cells. Northern blot analysis was performed using our cDNA probe for human DPP IV that presents more than 94% homology with rat DPP IV cDNA. Results clearly show that there is approximately seven times less DPP IV mRNA in crypt cells than in villus cells. We conclude that the differentiation-dependent expression of DPP IV in rat jejunum is primarily controlled at the mRNA level.