urea and ammonia Flashcards
What are the essential amino acids?
Met, Val, His (glucogenic)
isoleucine, phe (phenylalanine), threonine, tryptophan (Trp)
ketogenic: Leu and Lys
What amino acids are most required during periods of growth?
Arg and His
symptoms of ammonia intoxication
tremor (asterixis), slurring of speech, somnolence, vomiting, cerebral edema, blurry vision
causes of ammonia intoxication
acquired (liver disease) or hereditary (urea cycle enzyme deficiencies). causes excess NH4+, which depletes alpha-ketoglutarate, which inhibits TCA cycle.
Treatment for ammonia intoxication. Why is ammonia toxic?
limit protein in diet. give benzoate or phenylbutyrate, which bind amino acid and lead to excretion to decrease ammonia levels. give lactulose to acidify the GI tract and trap NH4 for excretion
N-acetylglutamate deficiency
N- acetylglutamate is a required cofactor for the carbamoyl phosphate synthetase I rxn which converts CO2 and NH3 to carbamoyl phosphate. this causes hyperammonemia. presentation is just like carbamoyl phosphate synthetase I deficiency but there will be an increased ornithine with normal urea cycle enzymes.
Ornithine transcarbamylase deficiency. Inheritance?
most common urea disorder. X-linked recessive (vs. other urea cycle disorders, which are autosomal recessive). remember that ornithine transcarbamylase is the enzyme that takes carbamoyl phosphate and ornithine to make citrulline. interferes with the body’s ability to eliminate ammonia. usually in first few days of life, though it may be late onset. excess carbamoyl phosphate is converted to orotic acid
Findings for ornithine transcarbamylase deficiency
(remember- this enzyme takes ornithine and carbamoyl phosphate and converts to citrulline). see incr. orotic acid in the blood and urine (conversion of excess carbamoyl phosphate), decr. BUN, hyperammonemia symptoms (asterixis, slurred speech, somnolence, vomiting, cerebral edema, blurry vision). No megaloblastic anemia (vs. orotic aciduria).
