Intestinal Absorption and the Elimination of Toluidine Blue O in the Rat

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Abstract
Toluidine blue appeared in the duodenum of pyloric ligated, Sprague-Dawley rats 5 minutes following intravenous injection. Ligation of the bile duct resulted in toxic symptoms and death when a 0.5% solution of the dye was given. Animals survived at lower concentrations and dye still appeared in the small intestine despite ligation and severance of the bile duct. Toluidine blue also was recovered from the upper intestine when both biliary and pancreatic secretion into the intestine was prevented, indicating direct passage of dye through the intestinal mucosa. Injection of toluidine blue into the lumen of the duodenum resulted in recovery of dye from the stomach, urine, and a ligated portion of the duodenum above the site of injection. This demonstrates absorption of dye through the intestinal mucosa. Dye appeared in excreted urine of intact, non-fasted rats as early as 20 minutes following intravenous injection and after longer intervals in operated, fasted animals. Dye continued to appear in the urine long after it could no longer be detected in the blood.