12. Enzymes and cardiac markers Flashcards
Why are enzymes measured?
- to identify diseases that occur as a result of abnormalities in enzyme concentration or function (e.g. inherited metabolic diseases)
- to detect tissue damage
- markers of therapeutic response or drug toxicity
- As reagents for measurement of other substances
Other causes of increased enzymes other than tissue injury?
Increased synthesis and decreased clearance
How can measuring enzymes show tissue damage?
- Enzymes are primarily found intracellularly
- However, small amounts of these intracellular enzymes are detected in plasma as a result of normal cell turnover
- Level of intracellular enzymes in the plasma will increase following tissue injury
- This is because the membranes become leaky in scenarios of tissue damage
If there is severe injury (necrosis), what will leak out into the circulation?
cytosolic and subcellular enzymes will leak out into the circulation
Why is measuring enzymes TIME-crucial?
- Level of intracellular enzymes in the plasma will increase following tissue injury.
- This is because the membranes become leaky in scenarios of tissue damage. If there is more severe injury (necrosis), then the cytosolic AND subcellular enzymes will leak out into the circulation.
- Therefore, measuring enzymes is TIME-crucial.
- Release of cytosolic enzymes happens first, followed by release of sub-cellular enzymes.
Are enzymes highly specific?
Relatively few enzymes are highly cell specific, most others are widely distributed in many organs and tissues
Some enzymes may occur as different iso-enzymes. Individual iso-enzymes are characteristic to certain tissues. How do you check whether a raised enzyme has come from a particular tissue?
You may try checking whether another enzyme released by the same tissue has also been raised (e.g. ALP and GGT)
What organs is alkaline phosphatase present in high concentrations in?
Liver, bone, intestines and placenta
What are pathological increases in ALP mostly due to?
Liver and bone diseases
What is an increase in bone diseases associated with?
Increased osteoblastic activity
If GGT is raised with ALP, what does this imply?
Implies that the ALP is coming from the liver
What can be used to separate out the isoenzymes?
Electrophoresis (bone specific ALP immunoassay is now available)
What are the causes of raised ALP?
Physiological causes include pregnancy - 3rd trimester (from placenta), and childhood - growth spurts.
Pathological causes more than 5 x upper limit of normal include: bone (Paget’s disease, osteomalacia) and liver (cholestasis, cirrhosis).
Pathological causes less than 5 x upper limit of normal include: bone (tumours, fractures, osteomyelitis), liver (infiltrative disease, hepatitis). NOTE: ALP is NOT increased in osteoporosis unless there is a fracture
Where is amylase produced?
Amylase is secreted by exocrine pancreas
In what condition is there high serum amylase activity?
In acute pancreatitis
What is the level of amylase in acute pancreatitis?
It is usually 10 x the upper limit of normal
Apart from amylase, what else is measured in acute pancreatitis?
Pancreatic lipase is also often measured because it is a good marker of acute pancreatitis
The salivary glands also produce an amylase isoenzyme. What is this raised in?
Can be raised in parotitis
What else apart from acute pancreatitis can increases in amylase be seen?
The salivary glands also produce an amylase isoenzyme (it can be raised in parotitis). Increases in amylase may also be seen with other causes of acute abdomen.