Are non-absorbable indicators of comparable value in the human stomach made abnormal by taurocholic acid?

1. The substances chromium-51 (51CrCl3) and phenolsulphonphthalein (phenol red; PR) were compared as non-absorbable indicators in the human stomach after alteration of ionic permeability by taurocholic acid. 2. Control and test solutions containing 10 mM taurocholic acid and indicators at pH 1 were instilled into the stomach and sampled immediately and after 15 min. The ratios of the initial and final concentrations of the indicators (Ci/Cf) were compared. 3. Correlation coefficients of the Ci/Cf ratios for the two indicators were 0 with 91 in control studies and 0 with 75 after taurocholic acid instillation; there was no significant difference between either indicator. During taurocholic acid instillation, Ci/Cf values tended to fall compared to controls. 4. In a smaller number of subjects in whom polyethylene glycol (PEG) was also measured as a non-absorbable indicator, results were similar to those obtained with 51Cr and PR. 5. 51Cr, PR and PEG are comparable indicators in the normal human stomach and when it is made abnormal by a lipid-soluble agent such as unionized taurocholic acid, though the correlation between indicators is reduced in the abnormal stomach. 6. No evidence of increased absorption of any indicator was found in spite of the increased ionic permeability produced by taurocholic acid.