Urea cycle enzymes and urea excretion during the development and metamophosis of Xenopus laevis

Abstract

1. 1. During the development of Xenopus laevis tadpoles, the amount of ammonia and urea excreted increased, rising especially sharply during metamorphosis, and dropping in the adult. The percentae of urea remained contant until after metammophosis, but increased in the fully grown toads. 2. 2. The arginine synthetase system and arginase both increased during metamophosis, reaching levels comparable to those in Rana angolensis. Carbomoylphosphate synthetase and orinithine carbamoyltransferase showed no increase, and remained very much below those of Rama. 3. 3. The regulation of urea synthesis in Xenopus is discussed.