Abstract
The opioid peptides βCMs are derived from milk β-casein in the intestinal lumen. Natural βCMs as well as the analog β[DAla 2, 4, Tyr 5]CM5-NH2 caused a naloxone reversible reduction in short-circuit current (Isc) when added to the blood side of the isolated stripped rabbit ileum, in Ussing chamber. After addition in the mucosal reservoir at the concentration of 10-4 or 10-3 M, the natural βCMs did not alter Isc. HPLC analysis of peptides and aminoacids revealed that they were hydrolysed in the mucosal reservoir and that they did not cross intact the tissue. In contrast, the analog, at the same concentration, remained active on Isc; it was not hydrolysed and it was transported intact across the tissue (Jms = 3.5 ± nmole/hr cm2 at 10-3 M). Furthermore, the protected analog collected in the serosal reservoir after crossing the tissue displayed an intact aminoacid composition and was active on Isc. These results indicate that gCMs are opiate agonists acting on electrolyte transport. Their action from the luminal side seems to depend on the transfer of the intact peptides from the luminal to the blood side where opiate receptors are located. This action is prevented by mucosal hydrolysis of natural peptides.
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Tomé, D., Dumontier, A., Hautefeuille, M. et al. Opiate activity and intestinal transepitheliai passage of β-casomorphin (β-CMs) in vitro. Pediatr Res 22, 217 (1987). https://doi.org/10.1203/00006450-198708000-00026
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DOI: https://doi.org/10.1203/00006450-198708000-00026
