Non-Protein Nitrogen Flashcards
Ammonia
NH3; used to make urea in the liver during the urea cycle
Azotemia
high concentration of urea in blood;
Coupled Enzymatic method
urea + 2H2O –> urease–>2NH4+ +CO32-; NH4+ + 2-oxoglutarate –>GLDH–>glutamate + H20;
creatine
formed in liver from arginine, glycine, and methionine; converted to creatine phosphate which is a high energy source
creatinine
formed from creatine and creatine phosphate in muscle; excreted into plasma at a constant rate; used to assess kidney function
creatinine clearance
a measure of the amount of creatinine eliminated from the blood by the kidneys; CrCl = U(cr)V(u)/P(cr)t
estimated glomerular filtration rate
eGFR(mL/min/1.73m^2) = 175 x (Scr)^-1.154 x (age)^-.203 x (0.742 if female) x (1.210 if African-american)
glomerular filtration rate (GFR)
volume of plasma filtered by the glomerulus per unit of time
gout
caused by hyperuricemia; too much uric acid in body and uric acid crystals form and build up in joints, fluids, and tissues
hyperammonemia
excess if ammonia in the blood; leads to brain injury and death; primary cause of neurologic disorders
hyperuricemia
abnormally increased plasma uric acid concentrations; gout, increased catabolism of nucleic acids (chemotherapy), and renal disease; toxemia in pregnancy (decreased excretion)
hypouricemia
severe liver disease, rarer than hyperuricemia; Fanconi syndrome, chemotherapy with inhibitors of purine symthesis;
decreases in plasma urea
low protein intake, severe vomiting and diarrhea, liver disease, and pregnancy; low urea N/creatinine ratio
protein-free filtrate
measurement of non-protein nitrogen; used in caraway method which oxides uric acid in this filtrate
uric acid
product of catabolism of the purine nucleic acids; relatively insoluble in plasma; at high concentrations can be deposited in the joints and tissues
decreases in plasma urea
low protein intake, severe vomiting and diarrhea, liver disease, and pregnancy; low urea N/creatinine ratio
measurement of uric acid
uric acid –>uricase–>allantoin +CO2+2 H2O2; difference in absorbance before and after incubation with uricase is proportional to uric acid concentration; protein cause high background; hemoglobin and xanthine cause negative interference
measurement of uric acid
uric acid –>uricase–>allantoin +CO2+2 H2O2; difference in absorbance before and after incubation with uricase is proportional to uric acid concentration; protein cause high background; hemoglobin and xanthine cause negative interference
Jaffe Reaction
creatinine + picrate –>red-orange complex; positive bias from ascorbic acid, glucose, glutathione, alpha-keto acids, uric acid, and cephalosporins
Jaffe with adsorbent
creatinine adsorbed onto fuller’s earth then reacted with alkaline picrate –> colored complex; improves specificity
Jaffe with adsorbent
creatinine adsorbed onto fuller’s earth then reacted with alkaline picrate –> colored complex; improves specificity
endpoint Jaffe method
sample heated in acid solution to convert creatine to creatinine for measurement
Creatine enzymatic methods
creatine kinase, pyruvate kinase, and lactate dehydrogenase are used to produce a colored product
clinical application of urea measurement
to assess renal function, hydration status, determine nitrogen balance, aid in renal disease diagnosis, verify dialysis
Urea N calculation (US)
1 mg urea N/dL x 1 mmol N/14 mg N x 1 mmol urea/2 mmol N x 60 mg urea/1 mmol urea = 2.14 mg urea/dL
Urea N calculation (SI)
mg/dL * 0.36 = mmol/L
Reference Intervals - Adult; plasma
Reference Intervals- Adult, Urine
12-20 g/d; 0.43-0.71 mol urea/d
urea nitrogen/creatinine ratio
used to differentiate cause of abnormal urea concentration
