THE PRODUCTION OF CHLORIDE-FREE SOLUTIONS BY THE ACTION OF THE INTESTINAL EPITHELIUM

Abstract

The ability of the kidney tubules to move salt from a region of low concn. to one of a higher concentration is also possessed by the small intestine of the dog (or cat). If an isotonic mixture of NaCl and some other relatively indiffusible salt is placed in a loop of the small intestine, the solution becomes practically chloride free in 1 1/2 hrs. This process is accompanied by the removal of some water from the intestine, an increase in the concn. of the indiffusible salt (in this case Na2SO4) in the intestinal fluid, and the appearance of small amts. of other blood constituents in the intestinal fluid. The process is not influenced by the cation if it is monovalent. A quantitative analysis of the net changes in the amts. of the ions present, indicate that the process consists of an almost complete separation of the NaCl from the Na2SO4, leaving an isotonic solution of the latter in the intestine. A simple Donnan equilibrium cannot explain this movement of NaCl. This intestinal preparation affords a convenient method of studying a type of salt impoverishment of general physiological importance.