Effect of Excessive Dietary Sodium Chloride upon Liver and Muscle Glycogen in the Rat

Abstract

Chaikelis, 1 in 1934, stated that the inverse ratio between blood chlorides and blood sugar was not a compensatory mechanism concerned with the maintenance of proper osmotic pressure relations. He suggested that the blood chloride change was associated with some phase of carbohydrate metabolism. Following his report an investigation was started in this laboratory to determine what effect variations in the amount of sodium chloride in the diet would have upon the deposition of glycogen in the liver and muscles of the white rat.

Methods. Series 1. Young male rats were divided into 18 groups consisting of three animals each, the majority of which did not vary in weight by more than 10 gm. One animal of each group was placed on a diet poor in chlorides, one was placed on a diet rich in chlorides, and the third received a control diet. The control diet consisted of casein 33 percent, agar agar 2 percent, Osborne and Mendel 2 salt mixture 4 percent, cod liver oil 2 percent, butter (unsalted) 7 percent, yeast 8 percent, and sucrose 44 percent. The chloride poor diet was of the same composition as the control diet except that the Osborne and Mendel “chloride free” salt mixture 2 was substituted for the complete salt mixture which was used in the control diet. The chloride rich diet consisted of a food mixture of the same composition as the chloride poor diet with the addition of NaCl to a level of 6.25 percent of the total diet. Distilled water was given ad libitum.

The animals were kept in individual cages over wire screens. The temperature of the room was controlled so that it did not vary from 75°F. by more than 4 degrees.

The diets described above were fed for 10 to 15 days, and the experimental period was terminated by a 24-hour fast, at the end of which time the animals were anesthetized with sodium amytal. The gastrocnemius muscle was exposed and frozen in situ by means of a mixture of solid CO₂ and ether, and the frozen muscle was removed and immersed in this mixture. The liver was then removed and frozen immediately in the same manner. The tissues were weighed in the frozen state and analyzed for their glycogen content by the method of Good, Kramer and Somogyi. 3 The glycogen hydrolysates were analyzed for their glucose content by the method of Shaffer and Somogyi. 4