Ammonium uptake and urea production in hepatocytes from lean and obese Zucker rats

The metabolic differences in vitro between genetic and dietary obese rats i n the uptake of ammonium and amino acids by the liver and their use for ure ogenesis have been assayed using hepatocytes isolated from Lean, Obese Zuck er (Genetic obese) rats and Dietary obese rats. The hepatocytes of genetic obese animals took up more ammonium and produced higher amounts of urea fro m ammonium and alanine than those of lean and dietary obese groups (2 and 5 times more respectively). In the lean and dietary obese groups urea synthe sis accounted for almost all the nitrogen taken up as ammonium. Thus, dieta ry and genetic obesity show a widely different handling of nitrogen, and th e genetic obese rats need to break down protein to maintain their hepatocyt e function.