Aim: 

To study the effects of orange juice on duodenal functions.

Methods: 

The proximal duodenum of anesthetized rats was perfused in situ for 60 min with three different hypertonic solutions, i.e., 150 mM NaCl + 400 mM D-glucose (A), 700 mM D-glucose (B) and freshly squeezed orange juice (C). All solutions had an osmolality approximately of 700 mOsm/kg H₂O. The effects of the aforementioned solutions were studied on epithelial paracellular permeability, motility, net fluid flux and luminal osmolality in the presence of the COX-2 inhibitor parecoxib.

Results: 

All animals responded to parecoxib with induction of duodenal motility. Perfusion with either solution A or B, but not C, depressed duodenal motility in a reversible manner. All hypertonic solutions induced net fluid secretion but the increase was higher in response to A (284 ± 19 ml/cm² h) than to B (187 ± 18 ml/cm² h) or to C (135 ± 51 ml/cm² h). Perfusion with solution C did not affect, while solution A or B increased epithelial paracellular permeability more than twofold. The capability of the duodenum to decrease luminal osmolality was markedly greater in response to A (-34.3 ± 2.0 mOsm/kg H₂O cm²) than to B (-24.4 ± 1.7 mOsm/ kg H₂O cm²) or to C (- 25.5 ± 3.4 mOsm/kg H₂O cm²).

Conclusions: 

Some unknown ingredient in orange juice reduces the hypertonicity-induced increase in epithelial paracellular permeability and prevents the inhibition of duodenal motility. The hypertonicity-induced increase in fluid secretion, and the decrease in luminal osmolality, is both dependent on luminal NaCl.