Non-Protein Nitrogen Compounds

Exam - 2

Breakdown of proteins and nucleic acid

Into creatinine, urea, ammonia, and uric acid

where is creatine synthesized?

Liver, pancreas, and kidney.

Which amino acids does creatine come from?

arginine, glycine, and methionine

where do creatine transported to?

muscle, brain, and other organs

Creatine converted to?

Phosphocreatine is used as an energy source (ATP)

Creatinine

Waste product of creatine and phosphocreatine

where is creatinine produced

Majority in muscle (blood creatine is proportional to lean muscle mass

where do creatinine travel to and get excreted in?

Travels to kidney and excreted in urine (good estimate of GFR)

Name two creatinine methodologies

Chemical (Jaffe) and Enzymatic

Specimen requirement for creatinine measurement

Serum or plasma. If plasma, avoid fluoride and ammonium heparin for the enzymatic method. Exercise and a high-meat diet increase creatinine

What chemical method is used to measure creatinine?

Jaffe reaction

What two main reagents react in the Jaffe reaction?

Creatinine + picric acid

What conditions are required for the Jaffe reaction?

alkaline pH ≈ 9.3

What color product is produced in the Jaffe reaction?

Orange-red

What factors affect the Jaffe reaction?

Picric acid concentration, pH, temperature, reaction time, wavelength.

Why is the Jaffe method not specific for creatinine?

other positive interferences such as protein ang glucose etc

What causes the jaffe reaction to be false-positive

Bilirubin and hemolysis (adding color)

What enzymes can be used in enzymatic test?

creatininase, creatinase, or creatinine deaminase

What two coupled reactions used to measure the product?

NADH → NAD⁺ or H₂O₂ → H₂O (spectrophotometrically)

Enzymatic vs chemical

Less interference from keto acids and cephalosporins than jaffe

T or F? Creatinine is endogenous

True

Why is creatinine ideal for clearance?

Filtered through glomerulus, little tube reabsorption, constant production.

creatinine clearance measured as?

rate → time. need both blood and urine concentrations

What is the GFR gold standard reference?

Inulin — zero reabsorption, but must be infused.

what does nomogram estimates?

BSA

what produces cystatin C

all nucleated cells at a constant rate

Urea synthesis rate depends on?

filtered through the glomerulus

what is the most abundant urine waste product?

BUN

Increased BUN

Excessive protein breakdown, High-protein diet, Pregnancy

Decreased BUN

Severe liver disease (cirrhosis)