Abstract
The metabolic fate of 14C-arginine was studied in mice. The highest concentration of radioactivity 60 minutes after intravenous injection of 14C-arginine was found in the pancreas, gastrointestinal wall, kidney and spleen. Moderate levels of radioactivity were observed in the adrenal, skin, hypophysis, thymus and testis, while radioactivity in the liver, lung, brain, blood and brown fat was low. Twenty-four hours later, the levels of radioactivity in the organs were markedly low.
The concentration of radioactivity in the trichloroacetic acid (TCA) -soluble fraction so minutes after injection was found to be highest in the kidney, moderately high in the muscle, pancreas and salivary glands, and low in the brain. In the TCA-insoluble protein fraction the highest concentration of radioactivity was found in the pancreas and intestinal wall 60 minutes after injection. The levels of radioactivity of the TCA soluble fraction in various tissues after 24 hours were markedly low but the incorporation of radioactive substances into proteins of the testis, muscle and brain were great.
Seventy-four per cent of the radioactivity administered was excreted in the 24-hour urine of mice. Approximately 75% of the urinary radioactivity was present in the form of 14C-urea and about s % was unchanged 14C-arginine. The cumulative 14CO2 exhaled in 24 hours was 8.3% of the administered radioactivity.
