NPNs Flashcards
The concentration of nitrogen-containing compounds
in this protein-free filtrate was quantified spectrophotometrically by converting
nitrogen to ammonia and subsequent reaction with ________ reagent to produce a yellow color
Nessler’s reagent (K2[HgI4)
Most abundant NPN to least
Urea Amino acids Creatinine Creatine Ammonia
the major excretory product of protein metabolism.
Urea
Small quantities of urea
(<10% of the total) are excreted through the:
GI tract & skin
Reference method for Urea
isotope dilution mass spectrometry (IDMS)
Analytic methods (Urea): Conversion of unionized urea to NH4 & CO2-3 results in increased conductivity
Conductometric
Analytic methods (Urea): Enzymatic reaction of NH4 2-oxoglutarate & NADH to form glutamate & NAD+
GLDH-couple enzymatic
Normal value of Urea Nitrogen (plasma/serum)
6-20mg/dl
Normal value of Urea Nitrogen (urine)
12-20g/d
An elevated concentration of urea in the blood is called
azotemia.
Very high
plasma urea concentration accompanied by renal failure is called
uremia or the
uremic syndrome.
is a result of reduced renal blood flow. Less blood is
delivered to the kidney; consequently, less urea is filtered.
Prerenal azotemia
Decreased renal function causes an increase in plasma urea concentration as
a result of compromised urea excretion.
renal azotemia
can be due to
obstruction of urine flow anywhere in the urinary tract by renal calculi, tumors
of the bladder or prostate, or severe infection.
Postrenal azotemia
The major causes of decreased plasma urea concentration include
low
protein intake and severe liver disease. Pregnancy
Urea: Increased
Urea N/C ratio: High
Crea: Normal
Prerenal
Urea: Increased
Urea N/C ratio: High
Crea: Increased
Postrenal
product of catabolism of the purine nucleic acids.
Uric acid
Renal excretion
accounts for about __% of uric acid elimination;
70
Nearly all of the uric acid in plasma is present as
monosodium urate.
Most other mammals have the ability to
catabolize purines to _______, a more water-soluble end product.
allantoin
based on the
oxidation of uric acid in a protein-free filtrate, with subsequent reduction of phosphotungstic acid in alkaline solution to tungsten blue. The method lacks
specificity.
Caraway method
Reference method for URIC ACID
IDMS
Drugs such as
__________ have been shown to increase values for uric acid.
salicylates and thiazides
may falsely
decrease results obtained by peroxidase methods.
High bilirubin
should not be used
for specimens that will be tested by a uricase method.
EDTA/Fluoride additives
a disease found
primarily in men and is usually first diagnosed between 30 and 50 years of age.
Affected individuals have pain and inflammation of the joints caused by
precipitation of sodium urates.
Gout
result of overproduction of uric acid, although hyperuricemia may be
exacerbated by a purine-rich diet, drugs, and alcohol.
hyperuricemia
which inhibits xanthine oxidase (EC
1.1.3.22), an enzyme in the uric acid synthesis pathway, is used for treatment.
Allopurinol
TRUE/FALSE: Patients with hemolytic or megaloblastic anemia may exhibit elevated uric
acid concentration.
TRUE
X-linked genetic disorder (seen only in males) caused by the complete
deficiency of hypoxanthine–guanine phosphoribosyltransferase (EC 2.4.2.8), an
important enzyme in the biosynthesis of purines.
Lesch-Nyhan syndrome
Mutations in the first enzyme
in the purine synthesis pathway, _______ (EC
2.7.6.1), also cause elevated uric acid concentration.
phosphoribosylpyrophosphate synthetase
result of decreased uric acid excretion is a common
feature of toxemia of pregnancy (preeclampsia) and lactic acidosis presumably
as a result of competition for binding sites in the renal tubules.
Hyperuricemia
Liver disease
Fanconi syndrome
Chemotherapy with azathiprine/6-mercaptopurine
Overtreatment with allopurinol
Hypouricemia
Plasma
creatinine is _____ related to glomerular filtration rate (GFR)
inversely
Creatine is synthesized primarily in the liver from ____ (amino acids)
arginine, glycine, and
methionine.
used to determine the sufficiency of
kidney function, to determine the severity of kidney damage, and to monitor the
progression of kidney disease.
Measurement of creatinine concentration
a measure of the amount of creatinine
eliminated from the blood by the kidneys, and GFR are used to gauge renal function
Creatinine clearance (CrCl)
Modification
of Diet in Renal Disease (MDRD) equation variables:
serum creatinine concentration, age, gender (sex), and
ethnicity
has been developed to calculate
eGFR in the pediatric population.
modified Schwartz equation
In this reaction, creatinine reacts with picric
acid in alkaline solution to form a red-orange chromogen.
Jaffe
reaction
used routinely despite these problems because it is inexpensive, rapid, and easy
to perform.
kinetic Jaffe method
Reference method for Creatinine
IDMS
may increase creatinine
concentration measured by the Jaffe reaction, especially at temperatures above
30°C.
Ascorbate, glucose, α-keto acids, and uric acid
May falsely elevate Crea when Jaffe reaction is used
cephalosporin antibiotics
causes a positive bias in some enzymatic
methods.
Lidocaine
known to affect both enzymatic
and Jaffe methods.
Dopamine
Plasma creatinine is a relatively insensitive marker and may not be measurably
increased until renal function has deteriorated more than ___%
50
produced in the deamination of amino acids during protein
metabolism.
5
It is removed from the circulation and converted to urea in the
liver.
Ammonia
is the most common cause of disturbed ammonia metabolism.
Severe liver disease
occurring most commonly in children, is a serious disease
that can be fatal. Frequently, the disease is preceded by a viral infection and the
administration of aspirin.
Reye’s syndrome
associated with inherited deficiency of urea cycle
enzymes.
Hyperammonemia
