Effects of Tonicity and Glucose on Intestinal Sodium and Water Absorption in the Rat

Abstract

The rat small intestine was perfused in vivo with solutions of varying sodium concentrations. Some solutions were hypotonic, glucose or mannitol was added to others to make them isosmotic. Sodium absorption was a function of sodium concentration from both isosmotic and hypotonic solutions. The increased water absorption from a slightly hypotonic solution was associated with increased sodium absorption. With a markedly hypotonic solution, net sodium entry into the lumen and decreased water absorption suggested disruption of membrane integrity. Glucose absorption was associated with increased sodium and water absorption. The increase in sodium absorption was greater than predicted from solvent drag by the volume of water associated with absorption of the glucose in isosmotic solution. Sodium influx was also increased in the glucose solution, indicating a relation between glucose absorption and sodium transport. All glucose effects were abolished by phlorizin.

Key-words:

• Absorption, intestinal
• sodium
• water
• phlorizin
• glucose
• tonicity