Relationship between Small-Intestinal Transit Rate and Intestinal Absorption of 14C-labelled Mannitol and 51Cr-labelled Ethylenediaminetetraacetic Acid in Healthy Subjects

Background: Although the small-intestinal transit rate is generally considered to influence the urinary excretion of markers of intestinal permeability, no study has until now formally addressed the importance of this influence in humans. Methods: Ten healthy subjects ingested a test solution containing 99mTc-labelled diethylenetriaminepentaacetic acid (99mTc-DTPA), 14C-labelled mannitol (14C-mannitol), and 51Cr-labelled ethylenediaminetetraacetic acid (51Cr-EDTA). After ingestion, the small-intestinal transit rate of 99mTc-DTPA was measured with the gamma camera technique. Urine was collected for time periods of 0-2 h, 2-4 h, and 4-6 h to measure the excretion of absorbed 14C-mannitol and 51Cr-EDTA. Moreover, the distribution volume and plasma clearance of 14C-mannitol and 51Cr-EDTA were determined in each subject. Results: A positive correlation was found between mean small-intestinal transit time and 0- to 6-h urinary excretion of 14C-mannitol. The study did not show any correlation between small-intestinal transit rate and 0- to 6-h urinary excretion of 51Cr-EDTA. Urinary excretion of neither 14C-mannitol nor 51Cr-EDTA was affected by distribution volume or urine volume. A positive correlation was observed between plasma clearance and 0- to 6-h urinary excretion of 14C-mannitol, whereas plasma clearance did not influence the urinary excretion of 51Cr-EDTA. Conclusions: Small-intestinal transit rate seems to have a significant effect on 0- to 6-h urinary excretion of 14C-mannitol, whereas small-intestinal transit rate does not influence the timed urinary excretion of 51Cr-EDTA.