Streaming potentials in the rat small intestine

Abstract

The effect of adverse osmotic pressure gradients on fluid transfer and electrical potential across the wall of rat everted small intestine sacs was investigated. Addition of mannitol to the mucosal fluid produced a potential change of 0.062 mV/m-OSmole and a decrease in fluid transfer of 0.015 ml/m-OSmole/hr. This is consistent with the production of streaming potentials due to fluid movement through negatively charged pores in the intestine. The solute-linked fluid movement did not pass through these negatively charged pores which were responsible for the streaming potentials. From the magnitude and polarity of the streaming potential a value of -50 mV was calculated for the zeta potential at the phase boundary in the pores. Streaming potentials were used to measure the equivalent pore radius, and a value of 4 A was obtained. Electro-osmosis may not be responsible for fluid transfer by the intestine, and the potential difference associated with hexose transfer may not be electrokinetic in origin.