Canine jejunal absorption and transit during interdigestive and digestive motor states.

To determine whether absorption varies during interdigestive and digestive motor states, an isolated, 75-cm segment of jejunum was perfused in each of five dogs with an isosmolar solution of 130 mM glucose, 80 mM NaCl, and [3H]polyethylene glycol (PEG). Effluent was collected from the distal stoma during 10-min intervals. Electrical activity of the segment was recorded concurrently. Transit times were assessed with boluses of [14C]-PEG. The dogs were studied during phase I, phase II, and phase III of the interdigestive myoelectric complex and also after a 200-g meal of liver. Absorption during fasting was greatest during phase I and least during phase III of the interdigestive myoelectric complex; feeding enhanced absorption over that seen during any phase of fasting. Transit was slowest in phase I of fasting and most rapid during phase III; transits during phase II of fasting and after feeding were roughly equal. Using indicator-dilution calculations, static volumes were greatest and mean flows slowest during phase I. Thus, jejunal absorption during fasting decreased as transit increased sequentially with the interdigestive myoelectric phases. However, after feeding, although transit time was similar to phase II, absorption was greater.