Lab D 6 Metabolic parameters; proteins Flashcards
Total protein concentration in blood, dependent on?
Total content in plasma (serum) is dependent on the intake, synthesis, transformation , catabolism and hydration status (dehydration, hyperdration)
Measurements of the total protein concentration of blood?
Chromatography, electrophoresis and refractometry
Normal range of total protein in blood
60-80 g/L
Where can we find smaller total protein content than the normal range?
Urine, cerebrospinal fluids, body cavity fluids or tissue homogenates
What method to see total protein content of fluids with lower than normal range values?
Lowry method, with Folin-phenol reagent is used
or
Ultrasensitive total protein method, where proteins are bound directly to stain molecules
Sensitivity of different methods measuring total protein content, whats the range of Biuret method or refractometry?
20-100 g/L
Biuret test
- Total protein measurement
- Measured photometrically
- Reagent contains: KNaSCN, CuSO4, KI and NaOH
- Chemical reaction: CO-NH + CU2+ + alkaline = purple complex
- Wavelength: 546 nm
Ultrasensitive total protein analysis
- Total protein in lower concentration
- Na-molibdate and pirgallol-red reagent forms a complex molecule by binding proteins
- Complex measured on 600nm wavelenght
- Sensitivity is 0.2-4 g/L
- Standards are 0.25, 0.5, 1.2 g/L
Refractometry
- Total protein (TP) analysis
- Light is refracted when reaching border of media with diff in specific gravity
- TP in blood plasma or serum is the biggest influencing factor on specific gravity (2-3 x higher conc than for eks ions)
- In refractometer the specific gravity of one media is given (glass), so the change in light refraction depend in quality of plasma/serum, also dependent on temperature
Refractometry, method
- Calibration, using distilled water
- 1 droplet plasma/serum on glass, close cover
- Looking in visor: the horizontal line on the scale tells us about the total protein content of blood sample
- Performed in room temp
Refractometry, false results?
- Less precise than spectrophotometry, but quicker
- Can be used in range of 25-95 g/L
- May give biased results in haemolysis or lipaemia
TP concentration of blood plasma depends on:
- Protein metabolism
- Water balance
TP concentration of blood plasma under dehydration
Total protein increases
TP concentration of blood plasma under hyperhydration
Total protein decreases
Protein fractions
- Major fractions are albumin, globulin and fibrinogen
- Fibrinogen in smallest amount
- Globulin is calculated by the difference of the TP and albumin concentration (Fibrinogen being 1/20 or 1/25 of TP)
Albumin measurement
- Method 1
- Albumin conc. can be measured by spectrophotometry
- Bromocresol green as reagent
- Reagent binds to albumin on pH 4.2 and forms blue-green complex -> measurable on wavelength 578nm
Albumin measurement
- Method 2
- Serum electrophoresis in combination with TP measurement
- More expensice than spectrophotometry, but used when protein fraction analysis is the basic aim
- Necessary to know TP because albumin is given in % of the total protein content of the sample
Changes in albumin concentration: decrease
- Decreased intake of proteins, decreased absorption (maldigestion, malabsorption)
- Decreased synthesis - liver failure, acute inflammation (it is a neg acute phase protein)
- Increased utilization - physiological conditions cause mild changes: pregnancy, work, exercise, production (milk, egg) and chronic diseases (chronic inflammation, neoplasm)
- Increased loss: via kidneys (protein loosing nephropathy; PLN), GI tract (protein loosing enteropathy; PLE), skin (burns), whole blood loss, sequestration into body cavities - NOT decrease of colloid pressure (cardiac disease, lymphangiectasia, portal hypertension, other vascular disorders, peritonitis ex. perforation in intestines, gall bladder, translocation of bacteria)
- Other relative decrease: hyperhydration (may be iatrogen, ex. excessive infusion)
Changes in albumin concentration: increase
Dehydration
Globulin measurement:
- Method 1
- Calculated roughly by the diff of TP and albumin conc. of serum
Globulin measurement:
- Method 2
- Serum electrophoresis is used if protein fraction analysis is the basic aim
- This method provides percentage values, so objective concentration (g/L) has to be calculated knowing the TP concentration