Studies of Small Bowel Adaptation After Intestinal Resection in the Rat

Abstract

Fasting rats were killed 5 to 6 weeks after a 50-cm resection of either proximal or distal small bowel or sham operation. Remaining intestinal segments appeared increased in both thickness and diameter. The mean villous height was greater in proximal and distal bowel remnants of resected animals than in comparable segments of sham animals of the same age and weight. The number of epithelial cells per μ of villous surface increased in proximal and distal villi. Lactase, sucrase, and maltase activities were significantly lower in homogenates of both whole mucosa and isolated villous epithelial cells collected from proximal remnants. With the exception of sucrase, disaccharidase activity was also significantly lower in whole mucosa and isolated epithelial cells collected from distal remnants. Isolated epithelial cells collected from proximal and distal remnants were incubated with C14-labeled glucose and C14-labeled leucine. The ratios of glucose or leucine counts per min per ml of cell water to counts per min per ml of incubation medium indicated active transport and were equal to ratios obtained from cells collected from control segments. However, when uptake of glucose and leucine was determined as a function of the number of cells, the net transport of both substrates was reduced in cells collected from the distal remnant. Glucose transport in everted gut sacs prepared from proximal remnants was significantly less than control segments. In the early steady state after small bowel resection, the remaining segment shows hyperplasia with an increase in the number of epithelial cells lining the villous surface. These presumably less mature and smaller cells have diminished disaccharidase and transport activity.