Gluconeogenesis in the kidney and liver slices of a lizard, Uromastix hardwickii.

1. The liver and kidney of the lizard Uromastix hardwickii have much higher contents of carbohydrate than have been reported for the corresponding rat tissues. Most of this carbohydrate still remains in the tissue even after a long preincubation. 2. Kidney slices of this lizard release both glucose and other carbohydrates into the medium. Hence glucose release alone, as demonstrated for rats, cannot be used as a good criterion of gluconeogenesis in this lizard. Moreover, the results obtained by glucose release did not agree with those in which the total carbohydrate was estimated in the slice and medium. 3. l-Glutamate, l-aspartate, dl-valine, l-proline, l-cysteine, l-lactate and succinate stimulated gluconeogenesis in the kidney slices, whereas citrate, l-alanine, l-serine, glycine, l-arginine and l-leucine did not. In liver slices only l-glutamate increased gluconeogenesis. 4. New carbohydrate formation in the kidney and liver slices after incubation with various substrates indicated that gluconeogenesis as well as the amino acid metabolism in this animal may be somewhat different from that of mammals.