The metabolism of subcutaneously injected [14N] urea in the cat

Abstract

When N15-labeled urea was injd. subcut. into a 2.0 kg. cat, 2.5% of the N15 was excreted in the urine in forms other than urea. The tissues contained N with slight, but significant excess of isotope. The fate of Nl5-labeled ammonia in the body was studied by measuring the distr. of N15 in the tissues and urine after subcut. injn. into a 1.2 kg. cat of N15 ammonium lactate in ten 4-hourly doses. Of the N injd. 54.2% was converted to N15-urea. In 40 hrs., at least 5% of the urea of the cat was broken down in the body. After admn. of N15-urea or N15-ammonium lactate the N of the gastric mucosa was not preferentially enriched with N15; this argues against the participation of gastric urease in local synthetic mechanisms.