For the in vitro studies the researchers used radio-reverse-phase high-performance liquid chromatography and mass spectrometry to analyze the degradation by PEP of 3H-labeled gliadin peptides 56-88 (33-mer). In the ex vivo studies the researchers added PEP and 3H-peptides together onto the mucosal side of duodenal biopsy specimens that were mounted in Using chambers, and the peptide transport and digestion were analyzed using radio-reverse-phase high-performance liquid chromatography.
The results indicate that in both in vitro and ex vivo studies the gliadin peptides were only partly degraded by 20 mu/ml of PEP. This concentration of PEP decreased the quantity of intact gliadin peptides (31-49 and 56-88) that crossed the intestinal biopsy specimens, but did not prevent the intestinal passage of toxic or immunostimulatory metabolites—for this the researchers determined that PEP concentrations of at least 500 mu/ml for at least 3 hours was required to achieve full detoxification of gliadin peptides, and thus prevent intestinal transport of active fragments—unfortunately this finding virtually eliminates PEP as a possible treatment option for those with celiac disease.
The researchers conclude optimistically, however: "After prolonged exposure to high concentrations of PEP, the amount of immunostimulatory gliadin peptides reaching the local immune system in celiac patients is decreased. These results provide a basis to establish whether such conditions are achievable in vivo (in living organisms)."