Time course of jejunal blood flow, O2 uptake, and O2 extraction during nutrient absorption

Experiments were performed on anesthetized dogs to determine whether responses of jejunal blood flow, arteriovenous O2 difference, O2 uptake (VO2), and glucose absorption to luminal placement of predigested food or glucose would change with time during 30- and 60-min placement periods and to determine whether bile alters the responses. During the initial 15 min, food, glucose, food plus bile, and glucose plus bile produced a 13, 10, 51, and 30% increase in flow, respectively. During the next 15 min, flow returned to control levels, while arteriovenous O2 difference significantly increased with food or glucose; with glucose plus bile, flow decreased to 28% above control. In the case of food plus bile, flow decreased to 26% above control at 30 min and returned to control 50 min after placement. Despite the fluctuation in flow, the increase in VO2, and glucose absorption stayed at a steady level throughout the entire placement period. Bile significantly enhanced the increases in both flow and VO2 produced by food or glucose, prolonged the hypermia, delayed the significant rise in arteriovenous O2 difference, and had no effect on glucose absorption. In conclusion, the relative contributions of blood flow and O2 extraction to the enhanced VO2 produced by luminal food and glucose change with time, and bile significantly alters the magnitude or time course of changes in the above three variables.