Intestinal villus blood flow measured with carbon monoxide and microspheres.

The purpose of the present study was to compare the small intestinal blood flow that equilibrates with luminal CO (FLco) with simultaneous determinations of villus blood flow measured by a recent modification of the microsphere technique. These studies, carried out in rabbits, showed that FLco closely correlated (r = 0.83) with villus flow measured with microspheres over a three-fold range of flows, and the mean rate of flow to the villi by both techniques was about 0.08 ml/min X g of intestine. Thus, FLco appears to be a measure of villus blood flow. Based on previous studies of inert gas uptake from the rabbit small intestine, it appears that absorption of readily diffusible substances in the rabbit can be represented by a simple two-component model: a flow-limited component in which substances equilibrate with villus blood flow and are carried away without subsequent countercurrent exchange, and a diffusion-limited component which presumably represents uptake by the blood flow of the crypt region or submucosa.