29 THE ROLE OF CHOLECYSTOKININ (CCK), FOOD AND SUBSTANCE P (SP) IN THE RELEASE OF INTESTINAL IMMUNOGLOBULIN A (IgA)

The ingestion of food augments the release of IgA in rat intestine. This study is intended to show that this phenomenon is mediated by CCK, and furthermore, that SP another of the gut-brain peptides also promotes a rise in intestinal IgA. Hooded Lister rats weighing 160-180 gm. were immunized with ovalbumin and Freund's complete adjuvant. On day 14 a booster dose was given. On day 21, a 10 cm. long segment of intestine was isolated 10 cm. distal to the pylorus and perfused with saline at a rate of 0.5 ml/2.5 mins. After a 10 mins. equilibration period, the CCK antagonist Proglumide(Milid Laboratories, Milano) 20 mg was injected i.v. to the “food” group. Ten mins. later 1 ml. of the protein hydrolysate Pregestimil (Mead Johnson Co. Evansville) was administered intragastrically. In the SP group, 25 μ m SP were administered i.v. Results: 1. In the “food” group, there was a significant rise of IgA after the administration of food (P < 0.05) and this was inhibited by the prior administration of the CCK antagonist. 2. In the SP group there was a significant rise of IgA at 2.5 mins. (P < 0.001) and this became significant again from, 10-20 mins. Conclusion: 1. Food induced rise of IgA in the intestine is probably mediated by CCK as it is inhibited by a CCK antagonist, and 2. SP is another neuropeptide promoting IgA release in the intestine. The effect of SP is much more prolonged than that of CCK.