Background: When compared with infant formula, human milk enhances gastric emptying in preterm infants. Hydrogen peroxide (H2O2) is present in large quantities in human milk that has an antimicrobial role for the mother and infant. In vitro adult rat studies suggest that H2O2 facilitates gastric motor contraction. Hypothesizing that H2O2 enhances gastric motility, we investigated its effects on the newborn rat stomach tissue.
Methods: Rat newborn and adult gastric fundic segments, or their smooth muscle cells, were used to evaluate the muscle response to H2O2 exposure. Tissue expression of Rho kinase 2 (ROCK-2; Western blot), its catalase activity, and H2O2 content (Amplex Red) were measured. H2O2 gastric mucosal diffusion was evaluated with Ussing chambers.
Results: In both newborn and adult rats, H2O2 induced gastric muscle contraction and this response was attenuated by pre-incubation with the antioxidant melatonin. H2O2 passively diffused across the gastric mucosa. Its effect on the muscle was modulated via ROCK-2 activation and inhibited by melatonin.
Conclusion: H2O2, at a concentration similar to that of human milk, promotes gastric motility in the rat. To the extent that the present findings can be clinically extrapolated, the human milk H2O2 content may enhance gastric emptying in neonates.