Nitrogenous excretion in Chelonian reptiles

Moyle, Vivien

doi:10.1042/bj0440581

Cited by 55 publications

(11 citation statements)

References 5 publications

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“…Thus rats and mice and some frogs excrete about 90% of their nitrogen as urea , and they have the higher enzyme activities found; semi-aquatic turtles excrete 50% of their nitrogen as urea (Moyle, 1949) and they have about half of the enzyme concentration of the completely ureotelic animals. The Mexican axolotl, a neotenic species, eliminates 20-40% of its nitrogen as urea (Munro, 1953;Sober6n et al 1959;Cragg, Balinsky & Baldwin, 1961) and the activities of its enzymes are in accordance with this fact.…”

Section: Resultsmentioning

confidence: 97%

“…The differential centrifugation of the livers of rat and Mexican axolotl was performed as described by Novikoff & Heus (1963 Percentage of N excreted Uric Urea acid 90 (Schimke, 1962b) 90 50 (Moyle, 1949) 50 (Moyle, 1949) 85 85 * These values represent the total arginine and urea produced in the incubation system (see the text). …”

Section: Methodsmentioning

confidence: 99%

“…The species chosen included clearly defined ureotelic animals where the urea enzymes are present and well-confirmed uricotelic animals where most of the corresponding enzymes are absent . The chelonian reptiles were selected because their nitrogen excretory pattern comprises ammonio-ureotelism and uricotelism, according to their habitat (Moyle, 1949), and the unique opportunity of studying the disappearance of a well-established metabolic cycle in a single biological Order is offered. In addition, a neotenic species, the Mexican axolotl, which is mainly ammoniotelic (Munro, 1953;Sober6n, Flores, Mora & Torres, 1959), was also included.…”

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confidence: 99%

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The Regulation of Urea-Biosynthesis Enzymes in Vertebrates

Mora¹,

Martuscelli²,

Pineda³

et al. 1965

Biochemical Journal

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1. Carbamoyl phosphate synthetase, ornithine transcarbamoylase, the arginine-synthetase system and arginase were measured in the livers of ammoniotelic, ureotelic and uricotelic animals. The chelonian reptiles, whose nitrogen excretory patterns vary according to the habitat, and the Mexican axolotl, a neotenic species, were also studied. 2. The levels of the activities of the first three enzymes mentioned correlate with the amount of nitrogen excreted as urea. 3. The terrestrial turtle, which excretes mainly uric acid, maintains a high arginase activity but has very low levels of the activities of the other three enzymes. 4. The first three enzymes of the urea cycle vary in the phylogenic scale in a co-ordinated manner, which suggests that they are under the same regulatory mechanism. 5. Urea formation from endogenous arginine in vitro has a low efficiency in the Mexican axolotl. 6. The induction of metamorphosis in the Mexican axolotl by the administration of l-tri-iodothyronine, which causes a shift from ammonio-ureotelism to complete ureotelism, is accompanied by an increase mainly in carbamoyl phosphate synthetase and also by an improvement in the efficiency of hydrolysis of endogenous arginine in vitro to give urea. 7. The results obtained by differential centrifugation of the urea-cycle enzymes in rat and Mexican-axolotl livers are presented. The location requirements for the integration of a metabolic cycle are discussed.

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Section: Resultsmentioning

confidence: 97%

Section: Methodsmentioning

confidence: 99%

mentioning

confidence: 99%

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The Regulation of Urea-Biosynthesis Enzymes in Vertebrates

Mora¹,

Martuscelli²,

Pineda³

et al. 1965

Biochemical Journal

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“…Aquatic turtles excrete mainly urea (6) and have the full complement of hepatic urea cycle enzymes including carbamyl phosphate synthetase and ornithine transcarbamylase (7), the enzymes responsible for intramitochondrial citrulline formation. Tortoises also have the full complement of urea cycle enzymes in liver but excrete more uric acid than urea (8). We now report that glutamine synthetase is a mitochondrial enzyme in liver of the tortoises Gopherus agassizii and G. berlandieri and that liver mitochondria from these two species form and release citrulline and glutamine during glutamate degradation.…”

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confidence: 69%

Avian and Mammalian Mitochondrial Ammonia-Detoxifying Systems in Tortoise Liver

Campbell

Smith

Vorhaben

1985

Science

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Liver mitochondria from the desert tortoise Gopherus agassizii and the Texas tortoise G. berlandieri contain glutamine synthetase, the enzyme used by birds and higher reptiles to detoxify ammonia generated intramitochondrially during amino acid catabolism. Tortoise mitochondria also contain carbamyl phosphate synthetase-I and ornithine transcarbamylase, the enzymes used by mammals for this purpose. Since chelonid reptiles have changed little since their divergence from the stem reptiles, this finding suggests that both systems were present in the latter before the emergence of the ruling reptile, avian, and mammalian lines of descent.

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“…Some aquatic species (Chelonia mydas) are predominantly ammonotelic (2), whereas semiaquatic species such as Pseudemys scripta elegans are ureotelic (1,6). Desert turtles excrete primarily uric acid (5). In humans, who are uricotelic, the N-substituted xanthines are highly metabolised by N-demethylation and C8-oxidation into uric acid derivatives, which in turn are excreted via the kidney by glomerular filtration and active tubular secretion (7).…”

Section: Introductionmentioning

confidence: 99%

Excretion and metabolism of a series of xanthines by the turtlePseudemys scripta elegans

Vree¹,

Vree²,

Nouws

et al. 1989

Veterinary Quarterly

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SUMMARY The xanthines paraxanthine, xanthine, and uric acid are absorbed completely by the turtle Pseudemys scripta elegans and metabolised presumably into CO2 and NH3. No intermediate metabolites are excreted. Caffeine, hydroxycaffeine, theobromine, hydroxytheobromine, and hydroxyparaxanthine are absorbed and excreted in different amounts or percentages of the dose administered. Intermediate metabolites of these compounds are not excreted. The turtle Pseudemys scripta elegans may, therefore, be ammonotelic.

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Nitrogenous excretion in Chelonian reptiles

Cited by 55 publications

References 5 publications

The Regulation of Urea-Biosynthesis Enzymes in Vertebrates

The Regulation of Urea-Biosynthesis Enzymes in Vertebrates

Avian and Mammalian Mitochondrial Ammonia-Detoxifying Systems in Tortoise Liver

Excretion and metabolism of a series of xanthines by the turtlePseudemys scripta elegans

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