Comparison of the in vivo sodium-removing activity of various types of ion exchange resins in rats.

Abstract

ON exchange resins have now come into use for the control of sodium absorp- tion in various types of edema, and are being administered experimentally in some cases of hypertension. In fact, resins are proving effective in any sit- uation where restriction of gastrointestinal absorption of sodium is of impor- tance (Arnold,l Dock,2 Hay and Wood,3 Danowski and associateq4 Kahn and :Emerson," Martz, Kohlstaedt and HelmerG, i ). The resins in use at the pres- ent time have several disadvantages as therapeutic measures, i.e., large daily doses of an insoluble material; acidosis which, although generally compensated, may over1oa.d the kidneys; loss of sodium absorbing capacity of the resin due Male rats of the Wistar strain were used for all experiments. The animals were placed in metabolism cages, two rats to a cage, and given food and distilled water ad libitum. A standard ground rat diet was fed to all animals. Resin-containing diets were prepared by mixing the desired amounts of resin in this standard diet. Table I gives the composition of all the diets reported in this paper. These will be referred to in the text either by number or by the specific resin which is under consideration in that section. Food and water con- sumption and body weight were measured daily. Urine and feces were collected from each cage daily during test periods and pooled for three-day samples. The animals were main- tained on either the standard or test diet for seven days, then urine and feces samples were collected for two successive three-day periods. Each resin test was preceded and followed by a. test on the standard diet. The intake of food and resin was not controlled, but in general the rats compensated for the noncaloric resin by eating larger amounts of the resin-eontain- ing diets. Feces, urine, and food samples were analyzed for chloride, phosphate, sodium, and potassium. The use of distilled water in the drinking bottles precluded the necessity of analyzing the water except when the two liquid resins were tested. Urine chlorides were determined by the modified Volhard-Harvey titration method, and urine inorganic phosphate by the Fiske and Subbarow method. Urinary sodium and potassium were determined on suitably diluted samples using the Beckmann flame photometer. Feces samples were dried for t,welve to eighteen hours in an oven at 100" C. They were then ground and thoroughly mixed. Chlorides were determined on 2-gram samples of the dried feces by the open Carius method. For the determination of fecal phosphate, sodium, and potassium, a 500 mg. sample -__