Effect of fasting on rat duodenal and jejunal microvilli.

Duodenal and jejunal ultrastructural morphology and total serum alkaline phosphatase (ALP) activity were investigated in Wistar rats submitted to normal feeding, a 24 h fasting without or with access to sawdust or expanded polystyrene, and a 22 h fasting followed by a 2 h refeeding. Ultrastructural observation of duodenal and jejunal villous tips showed the occurrence of degenerating epithelial cells that were much more frequent in the epithelium of fasted rats. Refeeding and ingestion of sawdust or expanded polystyrene decreased the mean percentage of degenerating cells in the duodenum but not in the jejunum in comparison to plain fasted animals. Normal feeding produced the highest value of serum ALP activity. Refeeding as well as ingestion of sawdust or expanded polystyrene increased serum ALP activity values from those of plain fasted state: the difference being significant only for the refed group. It is concluded that: a) feeding, for both duodenum and jejunum, and refeeding and mechanical stimulation, just for the duodenum, increased proliferation, decreased apoptosis or facilitated desquamation of the epithelium; b) ALP increase in serum was induced by feeding and refeeding.