Abstract
Background: Bombesin, the amphibian analog of mammalian gastrin-releasing peptide, reverses total parenteral nutrition (TPN)–induced atrophy of gut-associated lymphoid tissue and increases intestinal and respiratory immunoglobulin A (IgA) levels. Structure-activity studies suggested that the biologically active portion of bombesin is a C-terminal heptapeptide (7AA). This study investigates the effect of 7AA on lymphocytes counts of the Peyer's patches (PP), the lamina propria (LP) and the intraepithelial layer (IE). Methods: Forty-eight male mice were randomized to receive chow (n = 13), TPN only (n = 9), TPN + 15 μg 7AA 3 times per day (n = 13) or TPN + 150 μg 7AA 3 times per day (n = 13). After 5 days of feeding, PP, LP, and IE lymphocytes were determined. Intestinal IgA levels were measured with ELISA. Groups were compared with ANOVA. Results: All TPN-fed mice lost more weight than mice fed chow (p < .04). Lymphocyte counts in PP, LP, and IE were significantly lower in the TPN group than in the 3 other groups but did not differ between the groups fed chow, TPN + 15 μg 7AA 3 times per day, or TPN + 150 μg 7AA 3 times per day. Intestinal IgA levels were higher in chow-fed mice (148.4± 16.9) than in mice fed TPN (98.4 ± 14.0, p = .008), TPN + 15 μg 7AA 3 times per day (96.9 ± 7.7, p = .003) or TPN + 150 μg 7AA 3 times per day (87.3 ± 6.7, p = .001). Conclusions: The C-terminal heptapeptide of bombesin prevented the TPN-induced decrease in intestinal lymphocyte populations but not the reduction in intestinal IgA levels.
A 7-amino acid component of gastrin-releasing peptide is capable of histologic effects upon the gut-associated lymphoid tissue of parenterally fed mice. Functional effects are not maintained, however.
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