Lactate is not a major product of glucose metabolism in the respiring jejunum perfused in the recirculation mode in vitro.

Yields of lactate from glucose absorbed from the luminal medium and extracted concurrently from the vascular medium of the perfused rat jejunum in vitro were half those previously reported from comparable glucose concentrations in the recirculated perfusion media. These low yields were obtained by maintaining perfusion medium flow rates and pressures pharmacologically at values found in vivo; permitting normal peristalsis; and restoring the depleted glyceric acid-2,3-bisphosphate and reduced deformability of out-dated blood-bank erythrocytes to normal physiological values before they were added to the vascular perfusion medium and equilibrated at 37 degrees C with air/CO2. Respiration rates are recorded for the first time in each perfusion experiment. A substantial fraction of glucose consumed in this and all earlier recirculation perfusion experiments in vitro has still to be accounted for.