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nonprotein nitrogens

clinically significant non-protein nitrogens

QuestionAnswer
What has the determination of npn in the blood been used to monitor? renal function
Concentration of nitrogen containing compounds was measured spectrophotometrically by converting nitrogen to ammonia and subsequent reaction with what reagent to form what color? Nessler's reagent. Yellow color.
NPN are the products of what types of catabolism? protein and nucleic acid
NPN in highest concentration in blood? Urea
Excretory product of protein and AA metabolism Urea
Synthesized in liver from ammonia and CO2 from the deamination of AA in urea cycle? Urea
Filtered by the glomerulus. 40% reabsorbed in tubules. Urea
Amount of urea reabsorbed depends on what? Urine flow rate and hydration
Conversion of BUN to urea multiply by 2.14
How much nitrogen does 60 grams of urea contain? 28 grams nitrogen
Refers to elevated levels of urea in the blood azotemia
Refers to high levels of urea accompanied by renal failure uremia
Pre-renal causes of azotemia Reduced blood flow->less urea filtered dehydration, shock, corticosteroid therapy, high protein diet, fever, CHF
Renal causes of azotemia decreased renal function. glomerular-nephritis, tubular necrosis, chronic renal failure, intrinsic renal disease.
Post-renal causes of azotemia urinary tract obstruction - stones, tumor, severe infection
Causes of decreased plasma urea decreased protein intake, late pregnancy, infancy, severe liver disease
Tests used to differentiate the cause of azotemia BUN and Creatinine
Normal BUN:Creatinine ratio 10:1 - 20:1
Pre-renal conditions have what levels of BUN and Creatinine. What ratio? increased BUN, Normal Creatinine. High BUN:Creatinine ratio
Post-renal conditions have what levels of BUN and Creat? What ratio? increased BUN, increased Creat. High ratio.
Conditions resulting in decreased BUN:Creat ratio decreased urea production. decreased protein intake, tubular necrosis, liver disease
First step in enzymatic methods for urea conversion of urea to ammonia in presence of urease
Glutamate dehydrogenase (GLDH) coupled reaction for urea kinetic method that measures rate of disappearance of NADH at 340nm.
NH4 + 2-oxoglutarate + NADH -> Glutamate +H2O + NAD+ GLDH coupled enzymatic reaction for urea
NH3+ + pH indicator -> color change indicator dye method for urea
Conductometric method for urea conversion of unionized urea to NH4+ and HCO3- results in decreased conductivity. Specific and Rapid.
Advantages of conductometric method specific and rapid. ammonia does not interfere.
NH4+ + 5NaOCl + 2phenol -(nitroprusside/OH-)-> indophenol + 5NaCl + 5H2O -indophenol colored. Berthelot Method for urea
What are disadvantages to Berthelot method? Non-specific. Sensitive to interference from endogenous ammonia.
Measurement of urea by condensation with diacetyl monoxime in the presence of a strong acid and an oxidizing agent. Forms diazine which is yellow and is measured at 540 nm
Disadvantages of diacetyl monoxime method / advantages toxic reagents, non-specific ammonia does not interfere.
o-Phthaldehyde and naphthylethylenediamine react with what to form a chromogen? urea
Proposed definitive method for urea isotope-dilution mass spectrometry
Reference method for urea urease/GLDH coupled enzymatic reaction
What inhibits urease and should be avoided for specimen collection? sodium citrate and sodium fluoride
Why should specimens for urea analysis be refrigerated? Urea is susceptible to bacterial composition
Specimens for urea concentrations plasma, serum, or urine
Reference ranges for BUN serum and urine 6-20 mg/dL and 12 - 20 g/day.
conversion of mg/dL to mmol/L multiply by 0.36
Who has slightly higher levels of urea? adults over 60 and males
Who has slightly lower urea levels? pregnant women and children
Synthesized in the liver from arginine, glycine and methionine creatine
What is creatine converted to after being transported to muscle and what is it good for? What enzyme involved? phosphocreatine - high energy source for muscle building. Creatine Kinase
How much creatine is converted to creatinine daily? 2%
Waste product of muscle metabolism creatinine
What is formed when creatine phosphate loses phosphoric acid or when creatine loses water. creatinine
How is creatinine excreted? filtered by glomerulus and excreted in urine
What is plasma creatinine conc. a function of? muscle mass, creatine turnover, and renal function
Causes of increased plasma and urine creatine muscular dystrophy, polio, hyperthyroidism, trauma
Is creatinine elevated in cases of increased creatine? creatinine is normal
Are plasma creatine levels elevated in renal disease? NO
Are serum creatinine levels affected by a high protein diet? Muscle mass? NO. Yes, proportional to muscle mass.
Why is Creatinine is a reliable indicator of kidney function as it relates to glomerular function? 1) It's filtered completely through glomerulus and not reabsorbed by nephron tubule 2) It's an endogenous substance
measure of the ability of the glomerulus to filter blood creatinine clearance
Equation for creatinine clearance urine creat x urine vol / plasma creat x 1440
correction factor for body mass x 1.73/A
plasma conc of creatinine is ______ to creatinine clearance inversely proportional
Reference Ranges for Creatinine Clearance Male: 97-137 mL/min per 1.73 m2 Female: 88-128 mL/min per 1.73 m2
What is the Jaffe reaction based on principle that creatinine reacts with picrate in an alkaline soln to form an orange-red complex.
Disadvantages of Jaffe nonspecific and subject to positive interference from acetoacetate, acetone, glucose, ascorbate,pyruvate, cephalosporins
Adsorbent for jaffe Fuller's Earth or lloyds reagent
Dry slide method for creatinine coupled enzymatic reaction using creatininase, creatinase, sarcosine oxidase, and peroxidase.
method for creatinine using reagent strip 3,5-dinitrobenzoic acid (DNBA) + creatinine = purple product
Interferences of dry slide method some + due to lidocaine. Not affected by acetoacetate or cephalosporins.
Proposed reference method for creatinine HPLC
Specimen collection for creatinine plasma, serum, or urine. Avoid hemolysis and icterus (esp Jaffe), refrig urine and adjust to pH 7
Major product of purine metabolism uric acid
where is uric acid synthesized and where excreted liver adn kidney
what form is nearly all uric acid in plasma monosodium urate ions
At what conc can urate in plasma form crystals and precipitate? >6.4 mg/dL
Disease states associated with hyperuricemia gout, increased metabolism of cell nuclei(chemotherapy), renal disease, hemolytic/megaloblastic anemia, Lesch-Nyhan syndrome, dietary intake of purines, G6PD def, toxemia of pregnancy and lactic acidosis
Clinical Significance of hypouricemia secondary to liver disease ro defective tubular reabsorption (Fanconi's syndrome), chemo with 6-mercaptopurine or azathioprine. Overtreatment with allopurinol
uric acid is readily oxidized to what in the presence of what allantoin in the presence of uricase
caraway method for urea oxidation of uric acid with subsequent reduction of phosphotungstic acid to tungsten blue at 650-700 nm. Lacks specificity.
what provides alkaline pH for phosphotungstic method sodium carbonate
spectrophotometric method for uric acid using uricase measures decrease in absorbance at 293 nm as uric acid is converted to allantoin by uricase
interferences in simple uricase method proteins reduce sensitivity. Neg interference from hemoglobin and xanthine
Coupled enzymatic reactions for uric acid measure hydrogen peroxide produced as uric acid is converted to allantoin.
What catalyzes the indicator reaction in uric acid coupled reactions peroxidase or catalase
Interference in peroxide coupled reactions bilirubin and ascorbic acid destroy peroxide. minimize with potassium ferricyanide or ascorbate oxidase
Uric Acid Ref Ranges Male: 3.5 - 7.2 mg/dL
Uric Acid Female 2.6 - 6.0 mg/dL
uric acid child 2.0 - 5.5 mg/dL
uric acid 24hr urine 250 - 750 mg/dL
uric acid increase or decrease with age, pregnancy, children, premenopause increase,increase,decrease,decrease
Specimen for uric acid plasma, serum, urine. separate from RBCs ASAP
Falsley increase uric acid salicylates and thiazides
Falsely decrease uric acid hemolysis, icterus
Deamination product of AAs due to work of digestive and bacterial enzymes on proteins in GI Tract Ammonia
Released from skeletal muscle in exercise ammonia
what happens to ammonia in liver consumed by parenchymal cells in production of urea
are plasma ammonia conc dependent on renal function no
what are high levels of ammonia associated with being neurotoxic and associated with encephalopathy
what is ammonia conc useful for monitoring progress of severe clinical conditions
High levels of ammonia seen in liver disease, Reye's syndrome (children treated with asprin for virus), Renal failure, inherited defects in urea cycle
all enzymes in urea cycle are deficient in inherited disorders except for argininosuccinase
ion exchange method for ammonia NH3 adsorbed onto Dowex 50 resin, eluted, and quantitated with Berthelot reagent
ISE method for ammonia measures change in potential as pH of ammonium chloride soln as ammonia diffuses across membrane
Enzymatic method for ammonia GLDH. measures decrease in absorbance at 340 nm as NADPH is reduced to NADP+
Adult ammonia ref range 11-35 umol/L plasma 10-107 mmol N/day
child ammonia range 40 - 80 umol/L (higher than adults)
Specimen for ammonia heparin or EDTA. Place on ice immediately. Centrifuge at 0-4C within 20min and remove plasma. Assay ASAP or freeze at -20C
errors causing increased Plasma ammonia levels smoking,ammonium salts, asparginase, barbituates, diuretics, ethanol, analgesics, hemolysis
errors causing decreased plasma ammonia diphenhydramine, lactobacillus acidophilus, levodopa, antibiotics
what causes reduction of nitrates to nitrites in urine gram negative bacteria
Created by: medtech