Effect of Cholera Toxin on Jejunal Osmoregulation of Mannitol Solutions in Dogs

Abstract

This study was done to determine how cholera toxin affects osmoregulation. Mannitol solutions of various concentrations were instilled into jejunal loops of anesthetized dogs, before and after treatment with toxin. Solutions of high osmolarity within the loops approach the osmolarity of plasma more slowly than do dilute solutions. After treatment with toxin adjustment is slower, and the concentration of Na⁺ is higher in all cases. Net movement of water and solute was out of the loop, or zero, in control studies, but always into the loop after treatment with toxin. The mechanism of adjustment in the control loop seems to be primarily absorption, while after administration of toxin it is primarily secretion. It is concluded that the relative inefficiency of the latter process accounts for the slower regulation.