Non-protein Nitrogen Compounds
No description yet. This curated deck is ready for daily study.
Card preview (24)
Describe non-protein nitrogen compounds
General term that can be used for different substances that have the element nitrogen in them, but are not proteins
Non-protein nitrogen compounds are products of what?
Products from the catabolism of proteins and nucleic acids which includes about 15 different substances (/compounds: NPN fraction)
Non-protein nitrogen compounds are used in evaluating
Renal function and excretion (plasma npns increased in renal failure; ordered as blood tests)
What are the most important NPNs
• BUN (Blood Urea Nitrogen) • Creatinine • Uric acid • Ammonia
Major components of NPN with plasma concenctration (%plasma npn)
• Urea: associated with urine and fertilizer (BUN: 45%) • Uric acid: increases with intake of protein (20%) • Creatinine (5%) • Creatine: component of whey protein (1-5%) • Amino acids (20%) • Ammonia (0.2%)
What replaced the measurement of NPN?
determination of blood urea nitrogen (BUN)
It is the nitrogenous end-product of protein or amino acid and nucleic acid metabolism which constitutes 45-50% of NPN
Urea
How is urea synthesized in the liver?
Synthesized in the liver when NH3 is removed and combined with CO2 (Ammonia is very toxic so it is converted to urea)
Other characteristics of urea
• Excreted by glomerular filtration and partially reabsorbed through renal tubules • Rises quickly as compared to creatinine • Majority excreted in urine • Most widely used screening test of kidney function
Normal value of urea
• Normal value: 10–50 mg/dL
Highest concentration of NPN in blood and a major excretory product of protein metabolism (processes which release nitrogen, which is converted to ammonia and synthesized again in the liver from CO2 and ammonia that arises from deamination of amino acids)
Blood urea nitrogen BUN=urea determination
BUN is excreted by what organ?
Kidneys • Filtered by the glomerulus but 40% is reabsorbed by the renal tubules • <10% of the total are excreted through the gastrointestinal tract and skin
Plasma BUN Concentration is determined by:
• Renal function • Dietary protein intake • Protein catabolism rate
[Clinical significance of BUN) Measurement of urea is used to:
• Evaluate renal function • Assess hydration status • Determine nitrogen balance • Aid in the diagnosis of renal disease • Verify adequacy of dialysis
Pre-renal causes (ie blood vessels) of Hyperuremia or increased BUN
(Sometimes translates into dehydration) • ↓ Renal blood flow (e.g. CHF & dehydration) • ↑ Protein catabolism (as in fever) • High protein diet • Corticosteroid drugs
Renal/within the kidney causes of hyperuremia have usually what
Co-morbidity with other diseases
Renal causes of HYPERUREMIA
• Acute and chronic renal failure (associated with diabetes mellitus) • Glomerular nephritis • Tubular necrosis • Malignant hypertension
Post-renal (outside the kidney) causes of HYPERUREMIA are usually associated with
Obstruction: • Urethral stones • Tumors of bladder • Prostate enlargement • Cervical cancer
A decrease in BUN is associated with
Hypouremia
Symptoms of hypouremia
• Liver failure or severe liver disease (lack of urea synthesis) • Severe vomiting and/or diarrhea • Decreased dietary protein • Increased protein synthesis (observed in pregnant women and children) • Malnutrition (e.g. Kwashiorkor) • Overhydration • Early and late stages of pregnancy
It is the elevated urea concentration in blood (>20mg/dL)
Azotemia
T or F: Azotemia is always due to kidney dysfunction
False
Very high plasma urea concentration accompanied with renal failure
Uremic Syndrome or Uremia • Urea crosses the blood-brain barrier which is used by the brain for energy (Leads to confusion, lethargy, and comatose) • Uremic pericarditis: presence of heart murmurs
What is the mechanism of azotemia in pre-renal causes?
Reduced renal blood flow > less blood is delivered to the kidney > less urea filtered (Anything that causes a decrease in functional blood volume (low blood pressure))