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Arginine metabolism in cat kidney
O Levillain1, P Parvy, A Hus-Citharel
1Laboratoire de Physiologie Cellulaire, CNRS URA 219, Collège de France, Paris.
The Journal of Physiology
|March 1, 1996
Summary
Cats cannot synthesize enough arginine due to low blood citrulline and high kidney arginase activity. This limits arginine production, making an arginine-free diet life-threatening for cats.
Area of Science:
- Veterinary Medicine
- Biochemistry
- Renal Physiology
Background:
- Arginine is essential for feline growth and survival.
- An arginine-free diet is life-threatening for adult cats due to hyperammonaemia.
- The kidney is a primary site for arginine synthesis in many species.
Purpose of the Study:
- To investigate if the cat kidney synthesizes arginine.
- To identify factors limiting renal arginine production in cats, including low citrullinaemia and arginase activity.
- To determine the specific nephron segments involved in feline arginine metabolism.
Main Methods:
- Microdissection of identified nephron segments from cat kidneys.
- Incubation of nephron segments with labeled citrulline (anabolism) and arginine (catabolism).
- Measurement of arginine, urea, and amino acids using enzymatic methods and HPLC.
Main Results:
- Cat blood exhibits very low citrulline concentrations compared to other species.
- Arginine synthesis is primarily localized to the proximal tubule, particularly the proximal convoluted tubule.
- Arginase activity is also restricted to the proximal tubule, increasing towards the medullary straight tubule.
Conclusions:
- The cat kidney has a limited capacity for in vivo arginine production.
- Low blood citrulline levels and high proximal tubule arginase activity contribute to restricted arginine synthesis.
- These findings highlight the critical dietary requirement for arginine in cats.