Ionic Conductivities in Gastric Mucosa under Osmotic Gradients

Abstract

The effect of osmotic gradients on the transmucosal ionic conductance, intracellular potential and the serosal-to-mucosal conductivity ratios of the ephitelial and oxyntic cells were explored. Transmucosal and intracellular potentials as well as the changes produced by transmucosal 0.1 mA/cm², 1 sec, current pulses were measured. In 10⁻⁴ M histamine-stimulated mucosae the transmucosal conductance is significantly (P < 0.001) reduced from 3.73 ± 0.09 mmohs/cm² obtained with isosmotic (231 mOsm/Kg of water) solutions at both surfaces to 3.17 ± 0.05 mmohs/cm² by using hyperosmotic (508 mOsm/Kg of water) solution at the mucosal surface. Simultaneously, the transmucosal electrical potential difference referred to the serosal surface significantly increases (P < 0.001) from −23.3 ± 0.5 mV to −26.6 ± 0.5 mV by effect of hyperosmotic solution at the mucosal surface. No significant changes (P > 0.05) in the short circuit current, the serosal-to-mucosal conductivity ratios of ephitelial and oxyntic cells and the intracellular potentials were produced by the use of hyperosmotic solution at the mucosal surface. These results suggest the possibility that hypertonicity at the mucosal surface affects mainly the paracellular pathway and in a less extent the transcellular pathway for diffusion.