ChemPath: Enzymes and Cardiac Markers Flashcards

1
Q

Where are most enzymes found?

A

Intracellularly

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two types of intracellular enzymes?

A
  • Cytosolic
  • Subcellular (within organelles)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

Describe the order of release of intracellular enzymes when cells are damaged.

A

Cytosolic are released first, followed by subcellular

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

In which tissues is ALP present in high concentration?

A
  • Liver
  • Bone
  • Intestines
  • Placenta
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What is an increase in bone ALP caused by?

A

Increased osteoblast activity

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What technique is used to separate isoenzymes?

A

Electrophoresis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

List some physiological causes of high ALP.

A
  • Pregnancy - 3rd trimester (from placenta)
  • Childhood - growth spurt
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

List some causes of very high ALP (>5 x upper limit of normal).

A
  • Bone - Paget’s disease, osteomalacia
  • Liver - cholestasis, cirrhosis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

List some causes of moderately raised ALP (< 5 x upper limit of normal).

A
  • Bone - tumours, fractures, osteomyelitis
  • Liver - infiltrative disease, hepatitis
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Describe the ALP levels in osteoporosis.

A

It is NORMAL unless there is a fracture.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Which markers are used in acute pancreatitis?

A

Amylase

Lipase

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

Where else is amylase found?

A

Salivary glands

NOTE: will be raised in parotitis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What are the three forms of creatine kinase?

A
  • CK-MM = skeletal muscle
  • CK-BB = brain
  • CK-MB = cardiac muscle
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Describe the manifestations of statin-related myopathy.

A

Can range from myalgia to rhabdomyolysis

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

List some risk factors for statin-related myopathy.

A
  • Polypharmacy (in particular, fibrates and cyclosporin and other drugs metabolised by CYP3A4)
  • High dose
  • Genetic predisposition
  • Previous history of myopathy with another statin
  • Vitamin D deficiency (increased risk of statin intolerance)
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

List some other causes of high CK.

A
  • Muscle damage
  • Myopathy (e.g. Duchenne muscular dystrophy)
  • MI
  • Severe exercise
  • Physiological (Afro-Caribbeans)
17
Q

What are two other uses of enzymes in clinical medicine?

A
  • Markers of therapeutic response and drug toxicity (e.g. TPMT activity should be measured before starting thiopurines (e.g. azathioprine))
  • Reagents to measure other substances (e.g. glucose oxidase is used to measure plasma glucose)
18
Q

List three cardiac enzymes that used to be used as markers of cardiac damage.

A

CK

AST

LDH

19
Q

Where are myoglobins found within cells?

A

Cytosol

20
Q

Where is CK-MB found within cells?

A

Within the mitochondira and nucleus

21
Q

Where are troponins found within cells?

A

Within the contractile apparatus

NOTE: there is also a free cytosolic pool of troponins

22
Q

Describe how troponin levels change with time following an MI.

A
  • Rise at 4-6 hours post-MI
  • Peaks at 12-24 hours
  • Remains elevated for 3-10 days
  • So, troponins should be measured at 6 hours and 12 hours after the onset of chest pain in a suspected MI
23
Q

Outline the diagnostic criteria for MI.

A

Typical rise and gradual fall in troponin or more rapid rise and fall in CK-MB with at least one of the following:

  • Ischaemic symptoms
  • Pathological Q waves
  • ECG changes suggestive of ischaemia
  • Coronary artery intervention

Pathological findings of acute MI

24
Q

How are biomarkers used when deciding whether to thrombolyse?

A

None of the current biomarkers rise quickly enough to aid decisions regarding thrombolysis (so it is based on clinical findings and ECG)

25
Q

What are the main biomarkers used in cardiac failure?

A
  • ANP - from the atria
  • BNP - from the ventricles
  • BNP is used to assess ventricular function and can be used to exclude heart failure (high negative predictive value)
26
Q

Define 1 international unit of enzyme activity.

A
  • Quantity of enzyme required to catalyse a reaction of 1 µmol of substrate per minute

NOTE: activity is affected by assay conditions such as pH and temperature (so reference ranges may differ between laboratories)