Effect of proximal transposition of the ileum on mucosal growth and enzyme activity in orally nourished rats.

To determine whether exposure to proximal intestinal contents per se is an adequate stimulus for ileal adaptation of the magnitude seen after jejunectomy, rats were prepared by transposing 30 cm of distal ileum to the duodenojejunal junction or by sham operation. One month after surgery, mucosal mass (wet weight, protein content, and DNA content) and digestive enzyme activities were measured in segments of small intestine and compared between the groups. Measurements of mucosal mass in transposed ileum more than doubled those in control jejunum (p less than 0.001). Mean enzyme activities/cm bowel length in transposed ileum approached or surpassed measurements in control jejunum. In contrast to the other enzymes studied, mean sucrase specific activities were similar in transposed ileum and control jejunum, values fivefold greater than that of control ileum (p less than 0.002). We conclude that exposure of ileum to proximal intestinal contents reproduces the adaptive response that follows jejunectomy, without requiring short bowel. Sucrase responds to this exposure in a unique fashion.