Zur effektiven intraluminalen Konzentration von Riboflavin und Pyridoxin in verschiedenen Darmabschnitten der Ratte

The study was designed to determine the intraluminal concentration of riboflavin and pyridoxine in different gastrointestinal segments of rats as a function of time after intragastric application of the vitamins. A semi-liquid diet with¹⁴C-riboflavin and³H-pyridoxine was delivered by tube. After a period of 30 minutes, 1, 2, 6, 12 or 24 hours, respectively, concentrations of the vitamins were determined by radiochemical methods in stomach, duodenum, jejunum and ileum. In the duodenum highest concentration of riboflavin (10.4 nmol/l) was reached 2 hours, that of pyridoxine (5.5 nmol/l) 1.5 hours after intubation. In jejunum maximum concentration of both vitamins -4.1 nmol/l riboflavin and 3.0 nmol/l pyridoxine - was found 1.5 hours after tube feeding. As discussed for riboflavin, precise information about the physiologically relevant intraluminal concentration of micro-nutrients in the absorbing intestinal segments is essential, especially if transport mechanisms have to be elucidated.