Bombesin: An activator of specific Aeromonas antibody secretion in rat intestine

The effect of bombesin (BBS) in modulating the secretion of specific Aeromonas antibodies in rat intestine was determined. Rats were immunized with the culture supernatant of Aeromonas hydrophila, isolate SSU. This culture supernatant contained a number of toxins that may be considered virulence factors. After 24 days of immunization, rats were anesthetized and a 10-cm intestinal segment was perfused with phosphate-buffered saline. The effluents were collected for measurement of IgA and IgG by the enzyme-linked immunosorbent assay. When compared with the effect of intravenous administration of normal saline in the control group, intravenous injection of BBS (20 μg/kg) in the experimental group caused a significant increase in rat intestinal IgA and IgG in perfusates. The stimulatory effects of BBS on the presence of IgA and IgG were depressed partially by proglumide, a receptor antagonist of cholecystokinin (CCK) and gastrin. Treatment with pentagastrin (250 μg/kg) accelerated intestinal secretion of IgA, but failed to stimulate intestinal IgG secretion. In addition, intravenous injection of CCK-8 (120 ng/kg) evoked the intestinal secretion of either IgA or IgG. These findings demonstrated that BBS, gastrin, and CCK can stimulate antibody secretion in rat intestine and the stimulatory effect of BBS may be mediated partially via release of CCK and gastrin. These results suggest that neuropeptides such as BBS and gastrointestinal hormones, eg, CCK and gastrin, may participate in the regulation of intestinal secretion of IgA and IgG antibodies, respectively, in rats.