SUMMARY
The small intestine of healthy adult Beagles was examined to determine whether subclinical abnormalities might exist that would be relevant to the use of Beagles in pharmacologic studies. Duodenal juice was obtained for qualitative and quantitative bacteriologic examinations; jejunal mucosa was taken for morphologic and biochemical investigation, and intestinal permeability was assessed by quantification of 24-hour urinary excretion of 51Cr-labeled edta after its oral administration. Comparisons were made with findings in healthy adult dogs of other breeds that served as controls. Small intestinal bacterial overgrowth was found in 14 of the 21 Beagles examined, and represented a mixed flora that included obligate anaerobic bacteria in 8 dogs and exclusively aerobic bacteria in 6 dogs. Intestinal permeability (percentage urinary recovery of 51Cr-labeled edta; mean ± sem) was considerably higher (P < 0.01) in Beagles with anaerobic overgrowth (37.6 ± 3.2%) or aerobic overgrowth (30.5 ± 4.8%), compared with Beagles with no overgrowth (17.3 ± 1.6%) and with controls (11.1 ± 1.0%). In Beagles, significant (r = 0.54, P = 0.03) correlation was observed between 24-hour urinary recovery of 51Cr-labeled edta and bacterial numbers in duodenal juice. Morphologic changes in jejunal mucosa were minimal, and specific activities of brush border enzymes were not significantly decreased, apart from aminopeptidase N, but activities of lysosomal and endoplasmic reticular marker enzymes were higher in the 3 groups of Beagles with anaerobic, aerobic, or no overgrowth, compared with controls. These findings indicate that apparently healthy Beagles can have bacterial overgrowth in the proximal portion of the small intestine, which is associated with enhanced intestinal permeability and may not be suspected by clinical examination or routine histologic examination of mucosa.
