Lab D 6 Metabolic parameters; carbohydrates Flashcards
Glucose
Glucose is the basis of the energy household, which can be detected in plasma. Hyper og hypoglycemias are detectable from the blood sample
The most frequent method of measuring glucose?
- Handheld glucometer, measure electric conductance in the fresh droplet of blood
- Older type: GOD/POD enzymatic method
Handheld glucometer
- Measure electric conductance in the fresh droplet of blood
- Electric conductance changes not only with changing glucose conc., but also influenced by ratio of cellular elements (mainly RBCs)
- Reason is that cells also conduct electricity, but have bigger resistance than plasma
- Glucometer is calibrated for physological cell counts, thus if anemia -> glucose will be measured lower (compared to GOD/POD spectrophotometry)
If patient has polycythemia, glucose measure is higher
Plasma glucose is quickly catabolized by the enzymes of the RBCs, so measure quickly after sampling, or avoid in vitro catabolism of glucose in blood samples, how?
- Store sample in cooled conditions until blood glucose is measured (2-4 C)
- Separate plasma from blood quickly
- Coagulate RBCs by 3% trichloric acetic acid
- Take blood samples in tubes containing NaF, which inhibits enolase in RBCs by the reaction between Mg and F
Biochemical reaction for glucose measurement is the GOD/POD reactiion:
Glu + H2O –glucose oxidase– = gluconic acid + H2O2
H2O2 –peroxidase– = O + H2O
O oxidises a stain (m cresol and aminophenasone) which has a reduced form of no color. The oxidation changes the color of the stain. Depth of colour depends on glucose conc.
This test is used for spectrophotometrical and refractometrical (urine strips) analysis
Causes for increased glucose concentration; transient increase
- laboratory errors (haemolysis, lipaemia, icteris)
- Stress (cats! Up to >15mmol/L)
- Food intake (dogs, humans)
- Xylazin effect
- Cranial trauma or inflammation (rabies, Aujeszkys disease)
- After/during administration of glucose containing fluid therapy
Causes for increased glucose concentration; constant hyperglycaemia
- Diabetes mellitus
- Hyperadrenocorticism and glucocorticosteroid therapy
- Progesterone effect (iatrogen or endogenous - insulin resistance)
- Enterotoxaemia (sheep)
Causes for decreased glucose concentrations
- Lab error (incorrect storage/transport of sample)
- Decreased energy status (ketosis of ruminants, growing pigs or baby pig disease, puppies small breed, starvation, strenuous exercise - hunting dogs, racing horses
- Insulin overdose (sometimes beta receptor blockers in heart insufficiency)
- Insulinoma
- Anabolic steroid effect
- Liver failure, terminal stage
- Acute liver failure (fast depletion of liver glycogen after a very short hyperglycaemic phase)
- Hypoadrenocorticism
- Septicaemia
- Hyperthyroidism
- Paraneoplastic syndrome
Intravenous glucose tolerance test
• Glucose i.v -> see response of insulin, are the receptors okay
• Exclude the stressors
• If two separate blood samples (from starved animal) is above 11mmol/L
• Test should not be performed if level is very high (>20mmol/L)
• test can be performed when animal is starved for 24h
• Dog: 1g/kg bw, 40% glucose
• Cat: 5mg/kg bw, 40% glucose
Infused for 30-45 sec
• Blood sampling at 5, 15, 30, 45, 60 min. after infusion
Intravenous glucose tolerance test, performed when we suspect?
Onset of latent diabetes mellitus or insulinoma
How fast should blood glucose be normalized after infusion test?
After 30-60 min of sampling point
Oral glucose test (glucose absorption test), if we suspect what?
Chronic bowel disease, exocribe pancreatic insufficiency
Or it can be used instead of i.v glucose tolerance test
Oral glucose test (glucose absorption test)
- Test can be performed when animal is starved for 24h
- blood sampling, then 2g/kg bw of 12,50% glucose solution is given orally
- Blood sampling at 15, 30, 60, 90, 120 min after administration
- Blood glucose should be increased twice as normal value at 30 min, and normalized at 120 min after oral administration
The evaluation of constant hyperglycaemia
- Glucose molecules in blood attaches to variuos proteins
- Glucose bound to alpha amylase -> bigger molecule, macroamylase
- Glucose bound to more than one protein -> ketoamines
- Glycated hemoglobin - measure average plasma glucose over time
• Glucose molecules in blood attaches to variuos proteins, for ex?
Alpha amylase, hemoglobin,
• Glucose bound to alpha amylase -> bigger molecule, macroamylase
Due to bigger size, it cannit be excreted via the kidneys, so it circulates in the blood for a longer time
• Glucose bound to more than one protein -> ketoamines
One of the known ketoamines is fructosamine. Its concentration is not influenced by a short term hyperglycaemia (ex stress in cats or food intake in dogs), but increase if it is long term. Its conc represents the glucose average conc in the 2-3 weeks period before sampling
Glycated hemoglobin types
Haemoglobin A1c, HbA1c, A1C or Hb1c
Glycated hemoglobin measurement
- Measured primarily to identify the average plasma glucose concentrationover prolonged periods of time
- It is formed in a non enzymatic glycation pathway, by exposure to plasma glucose
- As the sverage amount of plasma glucose increases, the fraction of glycated haemoglobin increases
- Serves as a marker for average blood glucose levels over the previous 2-3months prior to measurement
Ketons, why do they appear
Appearance of ketone bodies is due to energy deficiency in liver cells
- decreased intake of carbohydrates
- decreased insulin production (diabetes ketoacidosis)
Ketons, measurements
• Conc of acetone and acetic acid can be estimated bybRoss reaction, betahydroxy butyrate can not
• Ketone bodies, use Ross reaction (found on test strips)
• Ross reagent: nitroprussid-Na, (NH4)2SO4, Na2CO3
• contaminated by ketone bodies (acetone,acetic acid) -> from whitegrey to purple. Depth depends on conc of ketones
Drop om sample and wait one minute
Samples used for determination of ketone bodies
Milk (1mmol), plasma (3-5mmol), urine (10mmol)
Found concentrated in urine samples
Urea conc of milk and plasma
- Energy status of cattle (dairy cows) can be estimated by the urea concentration analysis from milk and plasma
- If rumen has energy deficiency due to decreased carbohydrate intake, NH3 level increase in rumen
- -> results in increased urea production by the liver
Urea conc of milk and plasma, numbers?
Milk: from 2-5mmol/L to 8-10mmol/L
Plasma: from 8-10mmol/L to 15-17mmol/L
