Continuous Radioactivity Monitoring of Perfusion in the Small Intestine of the Intact Animal

Abstract

The phenomenon of intestinal absorption and transport has been studied by a variety of techniques. Since in vitro studies are removed from the physiological state and since it is very difficult, if not impossible, to simulate the steady state in the living intact animal, various modifications of in vivo systems have been developed. We have reported [¹] an in vivo perfusion system in which continuous absorption studies can be carried out using a single anesthetized intact small animal (rat), permitting the determination of continuous absorption patterns from the intestinal lumen in the same living animal. Sampling is possible at any elected time interval. The system described is a recirculating one. We have described a modification of the system, a single-pass perfusion [²’ ³] of the lumen with no recirculation of the solution perfused. Both of the systems have certain limitations in their operation. In the recirculating system samples drawn from the mixed perfusate during the experimental period bring about a diminution of the total volume perfused. In the single-pass system samples can be collected over any selected time interval; however, the quantities of material which are required for analyses and the slight gradient in concentration can pose technical problems.