Urinary Amino Acid Excretion in an Experimental Nutritional Hepatic Fibrosis

Abstract

The changes in the livers of West African children suffering from kwashiorkor have been described in detail by WALTERS and WATERLOW (1954). Various groups of workers (RICH and HAMILTON, 1940;MACHELLA and MAGUIRE, 1941; SPELLBURG, KEETON and GINSBERG, 1942; MACDONALD, 1955; and MACDONALD and THOMAS, 1956) have employed dietary methods to induce a fibrous tissue reaction of a similar nature in the liver of animals. In view of the widespread belief that the low protein content of the diet is the major aetiological factor in the production of kwashiorkor, and that protein deficiency, inter alia, is also a feature in children who show the clinical picture of marasmus only, studies of the protein metabolism should prove to be of interest. In their study of an experimental nutritional hepatic fibrosis presenting many features comparable to kwashiorkor, MAC-DONALD and THOMAS (1956) found the same hepatic changes in rabbits whether they had been fed on a diet either high or low in content of protein provided there was an abundance of readily-available carbohydrate. The present work was undertaken to find out whether there was evidence of disorder of amino acid metabolism in response to these two diets and to what extent any changes in urinary amino acid output could be correlated with the hepatic changes. METHODSEight young adult rabbits'of similar weight but mixed breed were used in these experiments. The animals were divided into two groups, and studies were carried out initially with all the animals on a normal green food diet for a period of one to five months. Then one group was placed on a low protein diet while the other group received a high protein diet. Food and water were supplied freely and the quantity of food eaten was measured daily. Each animal was weighed weekly. Twenty-four hour collections of urine were made from each animal at fourteen day intervals, the animals being kept in metabolic cages. The volume, total nitrogen, sodium and potassium content were determined. Total nitrogen was measured by a modified Pregl microKjeldahl technique (PREGL, 1923), and sodium and potassium levels were determined by means of an Eel photoelectric flame photometer.Paper chromatography was employed as a means of studying the urinary amino acids. 8 ml. of the 24 hour urine was desalted by means of an ion-exchange resin (Zeo Karb. 225 H) contained in columns. The eluate from the columns was evaporated under reduced pressure and the amino acid residue was made up to 1 ml. with distilled water. Some of this concentrate was oxidized (DENT, 1952) and 20 [»l. of the non-oxidised concentrate and the equivalent of the oxidised concentrate were applied to 20 cm. square Whatman 3 MM papers 2 cm. from one corner. After an initial overnight run in a butanol-acetic acid mixture, a second run at right angles to the first was carried out in a phenol-ammonia mixture the following night. The papers were dried and the location of the amino acids was achieved by dipping the papers in 0.2 per cent, ninhydrin in acetone. The spots which ...