The breakdown of urea in cats not secreting gastric juice

Abstract

When (Cl4) urea was injected intravenously into anaesthetized cats not secreting gastric juice, whose ureters were tied, the isotope equilibrated within 1 hr. with the urea of the body. This was found to be dissolved in a volume of water ("urea space") corresponding to an average of 65% of the body weight and equal to the total body water of the cats. Of the (Cl4) urea injected, amounts were hydrolyzed which varied widely between different cats but were constant within any one expt. The amounts of urea broken down (average 41 u moles/hr.) were measured from the quantities of (Cl4) CO2 expired. It was calculated that this in vivo breakdown of about 0.5%/hr. of the body urea could not be due to physicochemical transformations, but that enzymic cleavage of urea must occur. Removal of the esophagus or all the abdominal viscera did not diminish urea breakdown. Although suspensions of only stomach, ileum, and esophagus, showed urease activity in vitro, the site of the urease responsible for the in vivo breakdown was not, therefore, located in the esophagus or abdominal viscera. Cats whose head and neck were removed before the injection of (Cl4) urea, hydrolyzed urea at less than 15% of the average rate normally observed, but the head and neck regions on their own could break down urea at higher rates. Washings of mouth, nasopharynx, and trachea, contained high urease activities. Urease activity was abolished by treating cats with a mixture of penicillin, Terramyxin, and sulfaguanidine. This mixture had no direct effect on urease in vitro or in vivo, but acted by removing urease-containing bacteria from the cats. It is concluded that the enzymic breakdown of urea in cats not secreting gastric juice is caused by urease of bacterial origin, situated almost entirely in the head and neck.