Non-Protein Nitrogens Flashcards
nitrogen compounds
protein
nucleic acids
non-protein nitrogen plasma concentrations
non-protein nitrogens
urea 45-50% amino acids 25% uric acid 10% creatinine 5% ammonia 0.2%
Blood Urea Nitrogen (BUN)
manipulation of ammonia from the break down of protein, conjugated into urea in liver
filtered by renal tubules w/ partial reabsorption
cannot be used in clearance testing bc of reabsorption
BUN concentration depends on
renal function - if damaged BUN will be high
perfusion - sluggish blood flow BUN will be high
protein content of the diet
rate of protein catabolism
azotemia (BUN increase)
pre-renal conditions
renal conditions
post renal conditions
Pre-renal conditions for BUN increase
increased protein degradation - increase protein in diet, stress, fever, major illness, cortisol therapy
decreased blood flow through kidney- dehydration etc
renal conditions for BUN increase
kidney diseases
inflammations
post-renal conditions for BUN increase
blockages, obstructions
severe infections of kidney
tumors of bladder
reasons for BUN decrease
low protein intake severe liver disease late in pregnancy infancy not as significant as increased BUN
BUN/ Creatinine ratios
normal ratio : 10-20
pre-renal BUN/creatinine increase ratio -creatinine is normal & BUN value is elevated
renal BUN/creatinine ratio normal- both markers are elevated but ratio is normal
post-renal BUN/creatinine ratio increased - rise in both but more in BUN
low protein diet - decreased ratio
BUN analysis
coupled enzymatic reation - urease
patient’s urea + urease enzyme –> ammonia & carboxyl group
ammonia -(GLDH)-> NAD+
NAD is read at 340 nm to get BUN concentration
BUN electrode method
urease breaks urea into ammonia & ammonia ions change conductivity of electrod
meter reads change in potential between standard & patient sample
calculates BUN in mg/dL
BUN specimens
avoid ammonia, Na-citrate, Na-fluoride in samples
don’t need to be fasting
avoid bacterial contamination ( produce urease)
use plasma or serum
urines need to be diluted by 10
Uric Acid
nucleic acid breakdown of purines (Adenine & guanine)
eliminated :
70% out kidneys
30% our GI
hyperuricemia
elevated uric acid
gout- joint inflammation, uric acid crystals
F-1-PA: fructose 1 phosphate aldolase deficiency will cuase an increase in uric acid
Lesch-nyhan syndrome -missing HGPRT & cannot break down nucleic acids in a way that they can be reuesd
hypouricemia
decreased uric acid
fanconi’s syndrome- tubule defect in the kidney & cannot reabsorb uric acid
drugs interfere w/ degradation process of nucleic acids & do not allow for uric acid to be formed
Uric Acid analyzer methods
enzymatic method using uricase uric acid from patient + uricase -> allantoin + peroxide+ co2 peroxidase reaction to make color rx interference for peroxidase : ascorbic acid, bilirubin etc
Uric Acid specimens
use heparinized plasma or serum NO EDTA
drugs like aspirin & thiazides - increase uric acid
lipemia, increased bilirubin, hemolysis etc- decrease uric acid due to interference
creatinine
produced from creatine degradation in muscle tissue
creatinine level depends on muscle mass
plasma creatinine is inversely related to GFR
eGFR
estimated GFR which accounts for age, gender, ethnicity
better indicator for early kidney disease
Creatinine levels (low & high)
low levels are not significant in normal patients
high levels associated w/ increased blood creatinine & decreased GFR
although kidneys can have a 50% loss before any inrease in creatinine levels appear
methods for creatinine analysis
kinetic jaffe reaction
colorimetric jaffe reaction
enzymatic reaction -automated methods
IDMS - isotope dilution mass spectroscopy
Creatininease reaction
patient’s creatinine + creatininase enzyme -> creatine
creatine + CK -> phosphorylated creatine + PK -> pyruvate + LD -> NADP+ which is read at 340 nm
Creatinine specimen
use plasma, serum, or urine
avoid hemolysis, icteric (high bilirubin) samples
fasting not required
high protein diet can cause transient increase in creatinine concentration
refrigerate urines - cut bacterial contamination
sources of error in creatinine reaction
ascorbate, glucose, alpha keto acids, uric acid
bilirubin - negative bias in reactions
ascorbate interferes w/ peroxidase rx
cephalosporin - increases creatinine levels in jaffe reactions
dopamine & liodcaine - cause positive bias in enzymatic reactions
Creatinine clearance calculation
VU/Px1.73/A V- 24 hour urine volume U-urine creatinine P-plasma creatinine A- body surface in meters2
BUN range
7-18 mg/dL
Creatinine range
male - 0.9-1.5 mg/dL
female - 0.7-1.3 mg/dL
uric acid range
male - 3.5-7.2 mg/dL
female - 2.6-6.0 mg/dL
