Influence of aging on the surface area of the small intestine in the rat

Abstract

The conflicting reports regarding the influence of aging on intestinal absorption are due in part to the lack of a valid measurement of the intestinal surface area. The surface area of the small intestine in male Sprague-Dawley rats (2.5 to 92 weeks of age) was measured by determination of the volume required to fill the bowel under standardized conditions of stretch and pressure, and by calculating the surface area using the volume and length of the bowel. The intestinal surface area of rats of differing ages varied from 82 to 171 cm 2. The intestinal surface area increased linearly with the age of the animals during the first 6 weeks of life. No further increase was noted in the intestinal surface area during the following 86 weeks of life. A strong linear correlation was found between the intestinal length and surface area in rats of all ages. In contrast, no relationship was found between the intestinal surface area and its dry weight or the animal's body weight. It is concluded that assessment of the intestinal surface area is simple and can be used interchangeably with intestinal length to express the absorptive data in the rat. This parameter is preferred to indirect measurements like intestinal dry weight or animal body weight. Moreover, both the surface area and the length fluctuate at their 6-week values and do not change significantly with the increasing age of the rats.