Effect of age on the secretory capacity of pig small intestine in vivo and in vitro.

The effect of age on the secretory response of pig small intestine to in vivo challenge by cholera toxin (CT) was investigated. The small intestine of 14-day-old pigs was more sensitive to CT challenge than that of 14-wk-old animals. In the 14-day jejunum CT-induced fluid secretion was five times that observed in the 14-wk tissue. Similarly, the 14-day ileum produced a fourfold higher secretion than the 14-wk ileum, although the magnitude of ileal secretion was markedly lower than that observed in the jejunum at the same CT dose. This reduced response to CT with age was not due to a reduced secretory capacity of the tissue, since supramaximal doses of prostaglandin E2 and theophylline induced a similar response in tissue from both age groups in vitro. We conclude that these results are consistent with the hypothesis that an antisecretory factor, which naturally inhibits fluid losses in enterotoxigenic diarrhea, is produced in older animals.