Changes in intestinal villi, cell area and intracellular autophagic vacuoles related to intestinal function in chickens.

1. Morphological changes in the intestinal villi, cell area and cell mitosis number in the duodenal epithelial cells were compared in cockerels fasted for 1, 2 and 3 d, and also when refed for 1 and 2 d after 3 d of fasting, to demonstrate whether these morphological changes are related to intestinal function. Alterations in the fine structure of vacuoles in epithelial cells were also examined in each group to investigate whether the vacuolar changes are associated with these morphological changes, and to obtain an index for judging the nutritional condition of the chicken intestine. 2. Fasting induced decreases in villus height, cell area and cell mitosis number, which recovered rapidly after refeeding, suggesting that these parameters are related to changes in intestinal function and may be useful for assessing intestinal function. 3. At 1 d of fasting, small electron-dense bodies appeared in the absorptive epithelial cells, some of them fusing with each other. As the fasting period increased, these small bodies developed to moderate-sized nascent autophagic vacuoles containing various kinds of electron-dense contents and finally became large autophagic vacuoles with electron-lucent contents. Some vacuoles showed positive acid phosphatase reactions, which indicated that they were lysosomal autophagic vacuoles containing hydrolytic enzymes. 4. After 1 d of refeeding the large autophagic vacuoles seen after 3 d fasting rapidly decreased to the small electron-dense bodies seen after 1 d of fasting. 5. These findings suggest that intestinal epithelial cells have the ability to digest their own cell components to supply nutrients during fasting by means of lysosomal active autophagic transport mechanisms: after refeeding, the epithelial cells return to the absorption of nutrients. 6. The present results demonstrate that the autophagic vacuolar changes are correlated with changes in intestinal villus height, cell area and cell mitosis number induced by fasting and refeeding; this indicates that autophagic vacuoles are a useful index of the nutritional condition of chicken intestine. The greater the number of electron-lucent vacuoles there are in the duodenal absorptive cells, the lower the nutritional condition of the chicken intestine.