[2S] UNIT 9.2 Uric Acid Determination Flashcards by JULIA CASSANDRA RECCION

Q

One of the NPNs present in the bloodstream

A

Uric Acid

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Q

Organ in trouble when there is elevation of NPNs in the bloodstream

A

Kidneys

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Q

Only NPN that tells that the liver is in trouble if it is elevated in the bloodstream

A

Ammonia

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Q

Toxic byproduct that needs to be converted to urea for detoxification

A

Ammonia

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Q

Other NPNs circulating in the plasma

Not considered as waste product

A

Amino acids

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Q

Other NPNs circulating in the plasma

● Waste products
● Body needs to get rid of

A

Urea, Uric acid, Creatinine, Ammonia

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Q

End product of purine catabolism

A

Uric Acid

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Q

End product of protein catabolism

A

Urea

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Q

T/F: Urea is higher compared to creatinine

A

T

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Q

Precursor of uric acid

A

Xanthine

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Q

Where is uric acid produced?

A

Liver

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Q

Xanthine is acted upon by what enzyme and to be converted to?

A

○ Acted upon by Xanthine oxidase
○ To be converted to uric acid

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Q

It is a waste product

A

Uric Acid

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Q

Main product of the catabolism of exogenous (dietary) and endogenous purine nucleosides (Adenine and Guanine)

A

Uric Acid

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Q

T/F: Most uric acids are reabsorbed and 1% is excreted

A

T

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Q

T/F: Decrease in serum uric acid is common

A

F; uncommon

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Q

T/F: Although uric acid measurement may assess kidney function, uric acid is not as reliable as that of urea and creatinine.

A

T

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Q

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS

1st organ

A

Liver

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Q

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS

■ Cells that make up the lobules
■ It is where uric acid is produced

A

Hepatocytes

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Q

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS

Functional unit of the liver

A

Lobules

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Q

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS

Very vascular organ riched with blood vessels

A

Liver

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Q

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS

In the liver, ______ synthesize the uric acid

A

Hepatocytes

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Q

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS

travels in the bloodstream in order for them to be disposed properly

A

Hepatocytes

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Q

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS

Urinary bladder → urethra (vary in size)

A

Inner Medulla

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HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS This network of blood vessels are connected to the kidneys

Hepatocytes

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS 3rd site

Kidney (Outer Cortex)

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS Produce uric acid (waste product) → throw it in the _____

blood

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS Calyxes and Pelvis → Drains in the ureter and urinary bladder

Inner Medulla

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS Functional unit of kidney

Nephron

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS T/F: We can live with only 1 nephron and 1 kidney

F; we cannot live with only 1 nephron

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS Each kidney contains approximately 1 million to ____ nephrons

1.5 million

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS ● Found in medulla ● Contains blood vessel

Nephron

HOW IT TRAVELS FROM HEPATOCYTE TO KIDNEYS ● Part of nephron that acts as a filter ● Tuft of capillaries

Glomerulus

Why is it reabsorbed if it is a waste product?

It uses raw material for the synthesis of purines

If the physician is requesting for uric acid, it means he/she is suspecting that the patient has inflammatory condition in the joints

Gout

Effective Chemotherapy = ↑ uric acid _ plasma

↑

CHEMOTHERAPY More cells destroyed _ uric acid

↑ (megalo & cancer)

● Men age 30-50 years old are more commonly affected ● Females: menopausal

Gout

● Decrease concentration of uric acid ● The cells that produces uric acid are destroyed

Liver Disease

● Decrease concentration of uric acid ● 90% of uric acid is reabsorbed in the proximal convoluted tubule ● There will be no reabsorption of uric acid

Renal / Tubular Failure

Mixture of enzymatic and chemical method

Method of Determination

Measure the reaction at an absorbance of _____

293 nm

Historical method for the determination of uric acid

Conversion of uric acid to allantoin

METHOD OF DETERMINATION Decrease in absorbance is _____ proportional to the concentration of uric acid

directly

Principle of the reagent used in the experiment: Uric acid + O2 + 2 H2O2 → allantoin + CO2 + H2O2

Uricase

In the presence of uricase, uric acid is converted to?

allantoin and hydrogen peroxide

Principle of the reagent used in the experiment: 2 H2O2 + 4-AAP + EHSPT → quinoneimine + HCl + 4 H2

Peroxidase

Under catalysis of peroxidase with amino-4-antipyrine (4-AAP) and EHSPT, hydrogen peroxide reacts to give a?

red-violet quinoneimine dye

hasten the oxidation of uric acid to allantoin

Uricase

Quinoneimine uses a light with a wavelength of ___ nm

540

T/F: Concentration of quinoneimine (indicator) is directly proportional to uric acid

T

T/F: ENZYMATIC ASSAYS ARE MORE SPECIFIC THAN CHEMICAL ASSAYS

T

BUA Main form in Plasma

Monosodium Urate

Principle of Caraway Method

Reduction-Oxidation Reaction

CLINICAL APPLICATIONS T/F: Confirm diagnosis and monitor treatment of gout

T

CLINICAL APPLICATIONS T/F: Prevent uric acid nephropathy during chemotherapeutic treatment

T

CLINICAL APPLICATIONS T/F: Assist in the diagnosis of renal calculi

T

CLINICAL APPLICATIONS T/F: Assess inherited disorders of pyrimidine metabolism

F; purine

CLINICAL APPLICATIONS T/F: Detect liver dysfunction

F; kidney

Based on reduction of phosphotungstic acid in alkaline solution to tungsten blue

CHEMICAL: Caraway

In carbonate solution (Na2CO3/OH-): uric acid + H3PW12O40 + O2 → allantoin + tungsten blue + CO2

CHEMICAL: Caraway

Non-specific and requires protein removal

CHEMICAL: Caraway

● Uses uricase enzyme to catalyze oxidation of uric acid to allantoin ● More specific and more commonly used

Enzymatic Methods

Measures the hydrogen peroxide produced as uric acid is converted to allantoin

ENZYMATIC: Coupled Enzymatic Reaction

Color produced is directly proportional to uric acid concentration

ENZYMATIC: Coupled Enzymatic Reaction

2 Sources of error in coupled enzymatic reaction

Reducing Agents - High bilirubin - Ascorbic acid / Vit C

Measures differentiation absorbance before and after incubation with uricase at 293 nm

ENZYMATIC: Spectrophotometric Assay

Difference is directly proportional to uric acid concentration

ENZYMATIC: Spectrophotometric Assay

2 Sources of error in spectrophotometric assay

Presence of protein Hemoglobin & Xanthine

OTHER METHODS Typically uses UV detection

High Performance Liquid Chromatography (HPLC)

OTHER METHODS ● Proposed candidate reference method ● Detects characteristic fragments following ionization ● Quantifies uric acid using isotopically labeled compound

Isotope Dilution Mass Spectrometry (IDMS)

Specimen used

Heparinized plasma, urine or serum

T/F: Heparin inhibits uricase enzymes

F; EDTA & Fluoride

Uric Acid Reagent Kit

Phosphate buffer (pH 7.0), EHSPT, Amino-4-antipyrine, Uricase, peroxidase, ferrocyanide, sodium azide

ASSAY REQUIREMENTS ● Wavelength: ● Optical path: ● Temperature: ● Read against ________

546 nm 1 cm 37° C reagent blank

HYPER OR HYPOURICEMIA Gout

Hyperuricemia

HYPER OR HYPOURICEMIA Treatment of myeloproliferative disease with cytotoxic drugs

Hyperuricemia

HYPER OR HYPOURICEMIA Hemolytic and proliferative processes

Hyperuricemia

HYPER OR HYPOURICEMIA Purine-rich diet

Hyperuricemia

HYPER OR HYPOURICEMIA Toxemia of pregnancy

Hyperuricemia

HYPER OR HYPOURICEMIA Increased tissue catabolism or starvation

Hyperuricemia

HYPER OR HYPOURICEMIA Lactic acidosis

Hyperuricemia

HYPER OR HYPOURICEMIA Chronic renal disease

Hyperuricemia

HYPER OR HYPOURICEMIA Lesch-nyhan syndrome (hypoxanthine guanine phosphoribosyltransferase deficiency)

Hyperuricemia

HYPER OR HYPOURICEMIA Fructose intolerance (fructose-1-phosphate aldolase deficiency)

Hyperuricemia

HYPER OR HYPOURICEMIA Drugs and poisons

Hyperuricemia

HYPER OR HYPOURICEMIA Phosphoribosylpyrophosphate synthetase deficiency

Hyperuricemia

HYPER OR HYPOURICEMIA Liver disease

Hypouricemia

HYPER OR HYPOURICEMIA Glycogen storage disease type 1 (glucose-6-phosphate deficiency)

Hyperuricemia

HYPER OR HYPOURICEMIA Defective tubular reabsorption (Fanconi syndrome)

Hypouricemia

HYPER OR HYPOURICEMIA Chemotherapy with azathioprine or 6-mercaptopurine

Hypouricemia

HYPER OR HYPOURICEMIA Overtreatment with allopurinol

Hypouricemia

CONCENTRATION OF STANDARD Plasma / Serum

6 mg/dL

CONCENTRATION OF STANDARD Urine

88 mg/dL

Conversion factor of mg to mmol/L

0.0595

REFERENCE RANGE PLASMA / SERUM Male a. 3.5-7.2 mg/dL b. 2.0-5.5 mg/dL c. 2.6-6.0 mg/dL d. 250-750 mg/day

a. 3.5-7.2 mg/dL

REFERENCE RANGE PLASMA / SERUM Female a. 3.5-7.2 mg/dL b. 2.0-5.5 mg/dL c. 2.6-6.0 mg/dL d. 250-750 mg/day

c. 2.6-6.0 mg/dL

REFERENCE RANGE PLASMA / SERUM Child a. 3.5-7.2 mg/dL b. 2.0-5.5 mg/dL c. 2.6-6.0 mg/dL d. 250-750 mg/day

b. 2.0-5.5 mg/dL

REFERENCE RANGE Urine 24h

250-750 mg/day