ROLE OF UNSTIRRED LAYER IN INTESTINAL-ABSORPTION OF PHENYLALANINE INVIVO

The appearance rate of l- and d-phenylalanine in the venous blood of rat jejunal loops in vivo is increased up to 60% if the intraluminal solution is mixed more efficiently by the simultaneous perfusion of air. The effect decreases as the luminal concentration is increased to 100 mmol/1. Thus, the apparent Michaelis constants are by 50% lower in the case of the reduced unstirred layer (26 to 17 for l- and 9 to 6 mmol/1 for d-phenylalanine). The enhancement of the absorption and the reduction of the Michaelis constants can be attributed to the reduction of the effective unstirred layer thickness by about 400-500 μm. © 1979.