Gary E. Stahl, Jane C. Fayer, Saidee C. Ling, John B. Watkins

Comparison of Nonabsorbable Markers Poly R‐478 and [14C]PEG‐4,000 for Use in Developmental Absorption Studies

  • Gastroenterology
  • Pediatrics, Perinatology and Child Health
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SummaryTo determine the utility of Poly R‐478, a stable, polymeric dye (MW, 40,000), as a nonabsorbable marker for studies in the developing small intestine, it was validated by comparison to carbon 14‐labeled polyethylene glycol, MW 4,000 ([14C]PEG‐4,000) in rats from 14 to 40 days of age. The recovery and quantification of Poly R‐478 from biological samples is simple and rapid compared to other nonradioactive nonabsorbable markers. In 40‐day‐old rats simultaneously given Poly R‐478 and [14C]PEG, total recoveries were similar, the percentages of the Poly R‐478 dose and the [14C]PEG dose recovered per segment were identical, and taurocholate absorption rates calculated using each marker were comparable. Recovery of Poly R‐478 from flushed intestinal segments, determined by a one‐step extraction, was equivalent to that of [14C]PEG in 40‐day‐old rats (96.5 ± 3.7% versus 102.7 ± 10.1%; NS) but was superior to that of [14C]PEG in 21‐day‐old rats (98.0 ± 6.2% versus 63.4 ± 5.5%; p < 0.001) and 14‐day‐old rats (97.8 ± 6.7% versus 56.7 ± 12.6%; p < 0.001). Within each age group, the distribution of Poly R‐478 within the intestine was similar to that of [14C]PEG. In addition, total taurocholate absorption in the presence of Poly R‐478 was comparable to that in the presence of [14C]PEG. Complete recovery of Poly R‐478 from a suspension of liver particles and from mixtures with two commercial infant formulas was demonstrated in vitro, suggesting that Poly R‐478 may be used when foods are present in the intestine. Poly R‐478 is an effective and easily measured nonabsorbable marker and allows for development absorption studies utilizing two radiolabeled substrates.

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