The C-terminal heptapeptide of bombesin reduces the deleterious effect of total parenteral nutrition (TPN) on gut-associated lymphoid tissue (GALT) mass but not intestinal immunoglobulin A in vivo

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 microg 7AA 3 times per day (n = 13) or TPN + 150 microg 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 microg 7AA 3 times per day, or TPN + 150 microg 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 microg 7AA 3 times per day (96.9 +/- 7.7, p = .003) or TPN + 150 microg 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.