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11. Ammonia and Uric Acid


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What are the 2 main sources of ammonia?
1. Intestinal bacteria
2. oxidative amino acid deamination
Where does Urea come from?
Purine breakdown - Adenosine and Guanosine
By what 2 ways does Ammonia get removed from the body?
1. Urea production
2. Excretion
What disease states are associated with Ammonia over-production? (3)
1. Liver disease
2. Reye's syndrome
3. Inborn errors of metabolism (in the urea cycle)
What disease states are associated with overproduction of urea? (6)
1. Gout
2. increased nucleoprotein catabolism
3. Decreased renal function
4. Inherited defects
5. Chemo
6. Diet
What 4 methods can be used to determine Ammonia concentration?
1. Diffusion
2. Ion-exchange
3. Ion-selective electrode
4. Enzymatic
What wavelength is NADH measured at?
What 2 methods can be used for measuring Urea?
Colorimetric (tungsten blue)
Enzymatic (uricase)
What products can be measured in the uricase method for urea?
Allantoin - at 290 nm
NADH - at 340 nm
In what 3 ways is Ammonia neurotoxic?
1. Causes glutamate depletion
2. Causes cell toxicity
3. Produces a proline analogue
What 2 enzymes are involved in Ammonia EXCRETION?
-Glutamine synthetase
Why is Reye's syndrome associated with Ammonia buildup?
By taking aspirin after a virus, it reduces the ability to create Urea from NH3
What cycle do inborn errors of NH3 metabolism affect?
The urea cycle - therefore, there is ammonia buildup.
What 2 preanalytic variables can affect Ammonia measurement?
-Increased protein diet
-Extreme exercise
Regarding Uric Acid disease states, what 3 inherited disorders are related to it?
-Metabolism defects
-Lesch-Nyhan syndrome
-Defective renal tubular transport of Uric acid.
What in general causes an increased Uric Acid?
Increased purine breakdown
What 2 purines?
-the components of DNA/RNA!!!

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