In vitro studies on ammonia and urea formation by tissues.

This investigation was undertaken in the hope that light would be thrown on the subject of desaminase action by the various tissues of the body. The subject is in a more or less unsettled state, some workers 1 even disclaiming a true deaminizing action in tissues, believing that the ammonia production is due to deami-dase action. Still others 2 take the view that the amino acids instead of yielding ammonia, are attacked in the carbon chain itself, thus being broken down and oxidized, the products formed producing cyanic acid which can be converted into urea by the addition of ammonia formed by deamidase action.

In this work an attempt was made to study the action of ammonium salts, or of mixtures of amino acids and peptides, or of amino acids alone upon ammonia and urea formation or utilization by tissues in vitro.

The tissues used were obtained from recently killed dogs or from the abattoir, in this case using hog tissue. These were minced as soon as possible, mixed with a buffer phosphate Solution and after an hour the juice was filtered and pressed out. Of this well mixed fluid, 25 cc. portions were taken and incubated with the additions referred to. All the necessary control estimations were made and the methods used were critically studied before using them on the problem. The tissues studied were liver and kidney.

The main observations made are as follows:

1. Ammonium salts added to the tissue extracts inhibit ammonia production. The chloride is most inhibiting. The lowered ammonia production is usually accompanied by increased urea production. Thus, in four experiments ammonium as acetate, phosphate or lactate stimulated urea production, while in two experiments all the ammonium salts retarded urea formation, the phosphate being the least inhibiting.