Abstract 1. 1. Single administration of various doses (62.5, 125, 250, 500 μg/kg bodyweight) or multiple administration of a single dose (250 μg/kg body wt) of pentagastrin to fasted mice do not alter the protein and DNA content, nor the DNA synthesis in fundus of stomach, distal duodenum, and proximal jejunum. 2. 2. Pentagastrin has also been added at different doses into an organ culture of adult mouse duodenum or jejunum. 3. 3. The explants were taken from animals fasted for 24 or 48 hr before sacrifice. 4. 4. Protein and DNA content, protein and DNA synthesis, activities of several brush border enzymes and morphology have not been modified. 5. 5. Therefore, the drug does not seem to have a direct effect on the mouse intestinal mucosa. 6. 6. These observations are compared to results obtained from other species.