The Effect of Dodecylsulphate upon Net Sodium and Water Transport from Tied Jejunal Loops in Anaesthetized Rats

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Abstract
Into tied jejunal loops in rats solutions of sodium chloride or sulphate were instilled, with or without addition of sodium dodecylsulphate. The sodium salt concentration was varied, so that there was either a sodium concentration gradient from the plasma to the lumen, or a gradient from the lumen to the plasma. In the presence of surfactant, net secretion took place when there was a significant gradient from the plasma to the lumen, and net absorption when the gradient was reversed. With only a small gradient from the lumen to the plasma there was complete inhibition of net sodium transport. In principle, sodium in the presence of dodecylsulphate was transported along its concentration gradient. In control experiments, sodium absorption essentially independent of sodium concentration occurred. The results indicate that with dodecylsulphate, normal carrier‐mediated net sodium absorption is successively substituted by passive diffusion, as the surfactant dose‐dependently causes increased epithelial permeability to sodium. Less than 1.7 mM dodecylsulphate seemed to cause this effect.