Chemical Chemistry Flashcards
What is an Enzyme?
protein responsible for catalyzing a reaction
converting substrate into a product
organ specific
What effects Enzyme Activity?
molecules converted to different molecules
certain drugs and toxins
pH, temp, and concentration of enzyme
What are other chemicals/substances measured in blood?
hormones
electrolytes
other metabolites and metabolic by products of organ function
What are the purposes of measuring chemicals in blood?
-recognition and diagnosis of disease
-monitoring disease progress/activity
-prescription of proper therapy and
evaluating response to treatment
-pre surgical/pre anesthetic
What is the “Beer’s Law”?
concentration of a substance can be calculated by determining its ability to absorb light of a specific wavelength
What is Spectrophotemetry?
measures the amount of light transmitted through a solution
What is preferred when running tests?
serum
What anticoagulant do you use when using plasma?
heparin
When should you collect your samples?
prior to initiation of treatment (some meds inhibit enzyme activity)
Why should the animal be calm when collecting a sample?
epinephrine release
physiological response
causes splenic contractions
epinephrine inhibits insulin activity
What should the sample tube be labeled with?
patient name, owner name, animal ID #
date and time of collection
request form if sent to outside lab
What are the 3 types of factors that influence results?
pre-analytical
analytical
post analytical
What are factors that influence results?
time specimen interference pharmacologic/theraputic drugs chemical contamination patient influences improper handling of sample improper labeling of sample
Prolonged contact of RBC’s with serum decreases serum glucose at a rate of…
10% / hour
Time
- pre analytical
- glucose levels decrease (10%/hour)
- bilirubin is oxidized to biliverdin (exposure to fluorescent lighting)
- sample evaporation (increased concentration of values. TP, Na, K)
- bacterial growth decreases glucose concentration
Specimen Interference
analytical
hemolysis
lipemia
icterus
What causes hemolysis in a blood sample?
- drawn into a moist syringe
- mixed to vigorously after collection
- forced through a needle into a blood tube
- frozen (as whole blood)
- collected without cleaning alcohol from skin
What are the effects of hemolysis on test results?
- spectrophotometric influence
- fluid (water) from ruptured RBCs dilute sample, causing decrease concentration of blood constituents
- analyte release (increased TBIL, organic phosphate and others)
- enzyme release (ALT, AST, lactate dehydrogenase)
- reaction inhibition (pH change affects enzyme activity)
What are the effects of Lipemia on test results?
- light scattering (false elevations in TBIL, Hbg)
- volume displacement (false dec. esp. electrolytes)
- enhances hemolysis
What can you do to a Lipemic sample to remove fat?
refridgerate sample for a couple seconds
re centrifuge
What are the effects of Icterus on test samples?
- spectral interference
- bilirubin reacts with reagents, resulting in false decreases
Pharmacologic/Therapeutic Agents
- topical, oral, parenteral
- pre analytical
- analytical
What are drug effects on test results?
- decrease enzyme activity
- exogenous steroids reduce endogenous steroid levels
- increase in liver enzymes, BUN and glucose
- affects seen in electrolytes
- NSAID’s increase BUN and CREA
Chemical Contamination
- analytical
- use chemically pure tubes
- tubes don’t have to be sterile
Patient Influences
- pre analytical
- inherent=species, breed, age, gender
- controllable= stress level, exercise, drugs, estrous cycle
- time of last meal
What is affected with Post Prandial Samples?
increased glucose and lipemia increased GFR (glomular filtration rate)
Improper Handling of Sample
- pre analytical
- too warm = increased enzyme activity and destruction of chemicals
- complete analysis within 1 hour after collection
- frozen=mix thouroughly after thawing to avoid concentration gradients
Improper Labeling of Sample
post analytical
contributed to clerical/record keeping/labeling errors
Where are Immunoglobulins produced?
plasma cells
What are the functions of Plasma Proteins?
- form structural matrix of all cells, tissues and organs
- maintain osmotic pressure
- serve as enzymes
- act as buffers in acid/base balance
- serve as hormones
- coagulation
- defending body against pathogenic microorganisms
- serve as transport/carrier molecules
What are the Protein Assays?
total protein albumin globulins A/G ratio fibrinogen
How is Total Protein determined?
refractometer
What does Total Plasma Protein measure?
fibrinogen
albumin
globulin
What does Total Serum Protein measure?
albumin
globulin
What is Hypoproteinemia?
decrease in total protein
What causes decreases in Total Protein?
- liver disease (decreased synthesis)
- altered distribution (ascites)
- over hydration (hypervolemia)
- hemorrhage
- protein losing nephropathies/enteropathies
What is Hyperproteinemia?
increase in total protein
What causes increases in Total Protein?
kidney dysfunction
dehydration (#1)
increased synthesis of globulin
What is Albumin?
major binding/transport protein
responsible for maintaining osmotic pressure
What % of Albumin makes up TP?
35%-50%
What causes decreases in Albumin?
liver disease (#1) decreased dietary intake decreased intestinal protein absorption
What causes increases in Albumin?
renal disease
dehydration
How do you estimate Globulin concentration?
determining difference between total protein and albumin concentrations
What are the 3 categories of Globulins?
alpha globulins
beta globulins
gamma globulins
separated by electrophoresis
What are Alpha Globulins?
- transport and bind proteins and drug molecules
- include lipoproteins HDL and VLDL (cholesterol transport)
- chylomicrons (dietary lipid transport)
What are Beta Globulins?
include complement, transferrin, ferritin, LDL
What are the functions of Beta Globulins?
- iron transport
- heme binding
- fibrin formation and lysis
What are Gamma Globulins?
antibodies
How do you determine A/G Ratio?
dividing the albumin concentration by the globulin concentration
albumin / globulin
Alteration in normal A/G ratio is the first indication of what?
protein abnormality
What is the normal A/G ratio in dogs and horses?
> 1.0
What is the normal A/G ratio in cats and cattle?
<1.0
What causes an increase in Fibrinogen?
increased with acute inflammation or tissue damage
What is the most common method of Fibrinogen evaluation?
heat precipitation test
What are the Hepatobiliary Assays?
ALT AST SDH GLDH (AP)(ALP) GGT
What are the functions of the Hepatic Cells?
- metabolism of amino acids, carbs and lipids
- synthesis of plasma proteins
- conjugation of bilirubin
- synthesis of cholesterol
- production of bile
- detoxification
- drug metabolism (biotransformation)
- drug elimination
What % of liver function must be loss in order for clinical signs to show?
70%-80%
What predictable c/s do liver and gallbladder malfunctions produce?
- jaundice/icterus
- hypoalbuminemia
- hemostatic dysfunction
- hypoglycemia
- hyperlipoproteinemia
- hepatoencephalopathy
What is Liver Disease?
includes any process resulting in:
- hepatocyte injury
- chemostasis
What are causes of Hepatocyte Injury and Chemostasis?
hypoxia metabolic disease toxicoses inflammation neoplasia trauma bile duct obstruction
What is Liver Failure?
usually results from some form of liver disease
How is Liver Failure recognized?
- failure to clear blood of substances usually eliminated by the liver
- failure to synthesize substances normally produced by the liver
What are Hepatobiliary Assays designed to measure?
enzymes released from damaged hepatocytes
enzymes associated with cholestasis
hepatocyte function tests: measure substances eliminated and produced by liver
What tests are used to test for enzymes released from damaged hepatocytes?
ALT
AST
SDH
GLDH
What is ALT?
alanine aminotransferase
What species is ALT considered enzyme specific for?
dogs
cats
primates
What are other sources of ALT?
RBCs renal cells cardiac muscle skeletal muscle pancreas
What causes an increased ALT?
steroids
anticonvulsants
What is ALT screening used for?
liver disease
What is the increase, peak and return to normal time of ALT?
increases within 12 hours of damage
peaks within 24-48 hours
returns to normal in weeks
What is AST?
aspartate aminotransferase
AST is found in significant amounts where?
RBCs cardiac muscle skeletal muscle kidneys pancreas
What does an increased AST indicate?
non specific liver disease strenuous exercise IM injection muscle inflammation or necrosis hemolysis
What is SDH?
sorbitol dehydrogenase
What is GLDH?
glutamate dehydrogenase
Where are small amounts of SDH and GLDH found?
kidneys
small intestine
skeletal muscle
RBCs
What are disadvantages of SDH and GLDH?
unstable in serum (especially SDH)
tests not readily available in average vet clinics
What is Cholestasis?
stoppage/suppression of bile flow due to intrahepatic or extrahepatic factors, resulting in regurgitation of biliary substances into blood and jaundice
What tests are used for Cholestasis?
(AP)(ALP)
GGT
What is (AP)(ALP)?
alkaline phosphatase
(AP)(ALP) is present as an isoenzyme where?
osteoblasts chondroblasts intestinal epithelium placenta renal epithelium liver
How is (AP)(ALP) determined?
electrophoresis
What causes an increased AP?
osteosarcoma
What is the half life of AP?
3 days in dogs
6 hours in cats
What is GGT?
gamma glutamyltransferase
Where are the highest concentrations of GGT located?
liver
pancreas
kidney
Where is GGT also located?
mammary glands
intestine
muscle cell
What is GGT an excellent indicator for?
cholestasis in cattle, sheep and swine
What increases GGT?
cholestasis
acute hepatocyte injury
What do Hepatocyte Function tests test for?
levels of substances modified, produced and/or secreted by liver
What are the most common/useful Hepatocyte function tests?
bilirubin
bile acid tests
When will abnormalities show in Hepatocyte Function tests?
70%-80% of liver is damaged
What Hepatocyte Function tests are rarely performed?
dye excretion
ammonia tollerance
caffeine clearance
What does Bilirubin test measure?
circulating conjugated (direct bilirubin) and unconjugated (indirect bilirubin) bilirubin to pinpoint cause of jaundice
What causes an increase in conjugated bilirubin?
bile duct injury or obstruction
What causes an increase in unconjugated bilirubin?
excessive hemolysis
liver disease/failure
decreased albumin
What synthesizes bile acids?
hepatocytes from CHOL and conjugated with amino acids
What % of bile acid is reabsorbed into blood?
95%
What are potential sources of error when testing bile acid?
- inadequate fasting or spontaneous contraction (increased bile acids)
- prolonged fasting, diarrhea, GI malabsoption (decrease bile acid)
- lipemia
What are positive aspects of bile acid testing?
- may detect liver problems before c/s manifest
- good test to follow progress of liver disease treatment
- ELISA test is now available for in-house use
What is Cholesterol?
plasma lipoprotein produced primarily in the liver and ingested in food
What does Cholestasis do to cholesterol?
increases in some species because bile is a major route of CHOL excretion from the body
What can CHOL be used as a screening test for?
What can CHOL be used as a screening test for?
What hormone controls synthesis and removal of CHOL from the body?
thyroid hormone
What are other diseases associated with Hypercholesterolemia?
hyperadrenocorticism (cushing’s)
diabetes mellitus
nephrotic syndrome
What are the key functions of the kidneys?
- conserve or eliminate water and electrolytes in times of imbalance
- maintain normal blood pH by excretion or conservation of hydrogen ions
- remove end products of protein metabolism
- production of : rennin, EPO, prostaglandins
- aid in activation of vitamin D
What can be analyzed to evaluate kidney function?
blood
urine
What is BUN?
blood urea nitrogen
What are the Renal Assays?
BUN
CREA
BUN/CREATININE RATIO
What is BUN a end product of?
amino acid catabolism
What causes an increase in BUN?
when kidneys dont remove sufficent urea
What is Azotemia?
increased urea in circulation
What are causes of Azotemia?
alteration in blood flow through kidneys
urinary tract obstruction
dehydration
strenous excercise
What can affect BUN?
differences in rates of protein catabolism between males/females, younger/older animals, different species, and nutritonal status
What is the most accurate test for BUN?
photometric (vet test)
What is the least accurate tests for BUN?
chromatographic
What is CREA?
creatinine
What produces CREA?
formed from phosphocreatinine, a product of muscle metabolism that diffuses out of muscle cells into the blood
What is CREA proportionate to?
muscle mass; blood level should be constant
Where is CREA filtered?
through glomeruli
eliminated through the urine
What does CREA test?
glomerular function
What causes an increase in CREA?
lack of functional glomeruli
What is CREA also influenced by?
shock
bladder or urethral obstruction
What do disproportionate increases in BUN indicative of?
dehydration
What are other tests used to test kidney function?
- creatinine clearance tests (exo or endo)
- single injection inulin clearance (GF only)
- sodium sulfinilate (GF only)
- dye clearance (renal tubules)
- water deprivation tests
- vasopressin response
When is a Water Deprivation test used?
when PU/PD can’t be explained
What are contraindications of Water Deprivation tests?
dehydrated patient
azotemia
Most Pancreatic disturbances involve what?
exocrine function
What is the most common endocrine disturbance (Pancreatic)?
diabetes mellitus
What is the most common exocrine disturbance (Pancreatic)?
pancreatitis
Trauma or disease of the pancreas results in…
inflammation of pancreatic duct or cellular damage and leads to
- leakage or backup of digestive enzymes
- insufficent production of enzymes
What are the primary pancreatic enzymes?
amylase
lipase
trypsin
What is Acute Pancreatitis?
autodigestion of pancreas occurs when pancreatic enzymes are prematurely activated in the pancreas
What are causes of Acute Pancreatitis?
trauma hyperlipidemia hypercalcemia exposure to toxins idiopathic
What is Chronic Pancreatitis?
acute event must occur first
damaged pancreatic cells are replaced with tissue that cannot produce enzymes
What are the Exocrine Pancreatic Assays?
amylase lipase trypsin trypsin-like immunoreactivity pancreatic lipase immunoreactivity
Where is Amylase produced?
small intestine
salivary glands
What does Amylase break down?
glucose into starch
Increased serum amylase and lipase usually =?
pancreatic disease
What is diagnostic for pancreatitis?
3 fold increase in lipase and amylase
What are causes of increased amylase levels?
- enteritis
- intestinal obsruction
- intestinal perforation
- anything that causes a decrease in GF rate
What is used to test Amylase?
photometric
utilizes starch as substrate
What may decrease amylase activity?
lipemia
Why should EDTA not be used as an anticoagulant?
amylase activity requires calcium
What is the function of Lipase?
break down fatty acids and lipids
What filters Lipase?
kidneys
levels remain normal in early stages of pancreatic disease
What are other causes of increased Lipase levels?
renal dysfunction
hepatic dysfunction
steroids
What is used to test Lipase?
hydrolysis of olive oil in fatty acids
CPL (canine pancreatic lipase) snap test
What is Trypsin?
proteolytic enzyme that breaks down proteins into amino acids
Where is Trypsin more easily detected?
feces
What are the 2 methods of testing Trypsin?
test tube method
x ray film test
What is the Test Tube Method?
mix fresh feces with gelatin solution. wait… if 1. gel forms then NO trypsin (bad) 2. if no gel forms then trypsin present (good)
What is the X Ray Film Test?
place undeveloped strip of xray film in slurry of fresh feces. wait… if emulsion layer is removed, film will appear clear = trypsin present. if film remains unchanged, looks cloudy green/lavender, no trypsin
What is TLI?
trypsin-like immunoreactivity
Increased trypsinogen leaking into blood + circulating active trypsin=?
pancreatitis
What clears TLI?
kidneys and proteinase inhibitors
What is PLI?
pancreatic lipase immunoreactivity
What does PLI measure?
only lipase activity of pancreas
not affected by decreased GFR or gastritis
What are the 4 types of islet cells of the pancreas?
alpha
beta
delta
PP
Alpha
20% of cells
glucagon and somatostatin
Beta
80% of cells
insulin
Delta
1%
somatostatin
PP
1%
pancreatic polypeptide
What are the Endocrine Pancreatic Assays?
Glucose
Fructosamine
Glucose Tolerance Test
Insulin Tolerance Test
What is Hyperglycemia favored by?
glucagon, epinephrine, thyroxine, glucocorticoids, growth hormone
What is the hypoglycemic hormone?
insulin
What are the functions of Insulin?
encourages entry of glucose into cells/tissues for use
prevents exceeding the renal threshhold for glucose
What is the prefered anticoagulant for Glucose testing?
sodium fluoride
What is Fructosamine?
represents irreversable reaction of glucose bound to albumin
What causes an increase of Fructosamine?
persistant hyperglycemia (1-3 wks)
What test is used to confirm diagnosis of Diabetes Mellitus?
fructosamine
What can a Glucose Tolerance Test rule out?
diabetes mellitus
What is the procedure for the Glucose Tolerance Test?
- animal is fasted for 12 hours
- glucose administered IV
- measure blood/glucose at timed intervals and mapped as tolerance curve
What is the Insulin Tolerance Test?
checks responsiveness of target cells to challenge with IM or SC short acting insulin
What is the Insulin Tolerance Test used for?
determine appropriate insulin dose and monitor insulin therapy in diabetic animals
What is the procedure for the Insulin Tolerance Test?
- serum glucose is measured in a fasted animal prior to insulin injection (fasting blood glucose)
- feed animal before injection - every 30 minutes after injection, blood glucose is measured for 3 hrs and mapped as glucose curve
What can the Insulin Tolerance Test cause?
hypoglycemia
What does Gulcagon Tolerance asses?
hyperinsulinism
What is Hyperinsulinism usually caused by?
pancreatic cell tumor
What is the procedure for the Glucagon Tolerance test?
initial sample is taken prior to injection of glucagon. timed samples are taken 1, 3, 5, 15, 30,45,60 and 120 minutes after injection
What does the Insulin/Glucose Ratio test asses?
hyperinsulinism
