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23. Clinical Enzymology Flashcards

1
Q

Increased levels of intracellular enzymes in the serum caused by…

A

Cellular injury

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2
Q

Ranges of Injury (increased enzyme levels)
2-3 times upper limits of normal

A

Mild

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3
Q

Ranges of Injury (increased enzyme levels)
2-20 times upper limits of normal

A

Moderate

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4
Q

Ranges of Injury (increased enzyme levels)
Greater than 20 times upper limits of normal

A

Marked

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5
Q

Multiple forms of the same enzyme.
Catalyze the same biochemical reaction.
Have different biochemical and immunological properties.
Often have a different amino acid sequence or different amino acid composition and can be separated by electrophoresis.

A

Isoenzymes

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6
Q

Different tissues frequently contain isoenzymes with different proportions of subunits. So what can you do in case of cell damage?

A

In case of cell damage, the resulting particular serum pattern can indicate the affected organ.

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7
Q

Catalyzes a reversible reaction.
At high ATP levels, Creatine Phosphate (CrP) is formed.
At high CrP levels, ATP is formed using the energy-rich CrP.

A

Creatine Kinase (CK)
Kinase adds atp to something.

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8
Q

These three Creatine Kinase (CK) isozymes in serum are used as injury markers.

CK containers the two subunits B and M, leading to the three isozymes:

A

CK-BB (CK-1)
CK-MB (CK-2)
CK-MM (CK-3)

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9
Q

Mainly has CK-BB.
sCK-BB is elevated after CNS damage.

A

Brain

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10
Q

Has the highest percentage of CK-MB:
30% CK-MB (most CK-MB found in this organ) and 70% CK-MM.

SCK-MB and sCK-MM are elevated after myocardial infarction.

A

Heart muscle

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11
Q

Has 98% CK-MM and 2% CK-MB

SCK-MM is elevated in rhabdomyolysis or muscular dystrophy

A

Skeletal muscle

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12
Q

Tetramer of H and M subunits

A

Lactate dehydrogenase (LDH)

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13
Q

H4 in heart, RBC

A

LDH-1

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14
Q

H3,M1 in Heart and RBC

A

LDH-2

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15
Q

M4 in Muscle Liver

A

LDH-5

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16
Q

Severity is measured by the increase of LDH in serum following RBC destruction

A

Hemolytic Anemia

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17
Q

Leads to increase of heart LDH isozymes in serum which show a high LDH-1/LDH-2 ratio.

A

Myocardial infarction.

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18
Q

Since hemolytic anemia is a pathological state more erythrocytes become lyses. Since […] is the main isozyme present in erythrocytes, we will see an exaggerated increase in serum LDH.

Furthermore, we will also see an increase in serum: […], […], […]

A

LDH-2

Increase in serum: Hemoglobin, Indirect bilirubin, Reticulocytes

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19
Q

Timeframe in serum for MI markers
These levels peak after 24 hours

A

CK-MB

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20
Q

Timeframe in serum for MI markers
These levels peak after 48 hours

A

LDH

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21
Q

Total CK found in serum after an MI contains mainly [this] kind of CK but also the heart characteristic [this] kind of CK

A

After an MI contains mainly CK-MM but also the heart characteristic CK-MB.

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22
Q

A large […/…] ratio indicates a large area of damaged heart muscle.

A

CK-MB/total CK

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23
Q

One of two criteria for indication of an MI:
The CK-MB/total CK ration is > [..]% (Is larger than)

A

6%

24
Q

One of two criteria for indication of an MI:
The CK-MB/total CK ration is > [..]% and troponins are increased.

A

3%

25
Q

Proteins involved in muscle contraction

A

Troponins

26
Q

Specific troponins isoforms are measured as heart injury markers
Inhibition of actomyosin ATPase

A

Cardiac troponin I (cTnI)

27
Q

Specific troponins isoforms are measured as heart injury markers
Tropomyosin binding

A

Cardiac troponin T (cTnT)

28
Q

Myocardial infarction leads to myocardial cell death.
And […….] these two biochemical markers accumulate in blood and can be used for the diagnosis of an acute MI:

A
  1. Increase in cardiac troponins (cTnI or cTnT)
  2. Increase in CK-MB
29
Q

New method used to determine MI injury markers.
Used to measure CK-MB, cTnI, cTnT, and myoglobin

A

Elisa: Enzyme-linked Immunosorbent Assays

30
Q

Not all pts suffering from chest pain have MIs.
Chest pain also occurs in Severe exercise, acid reflux, intestinal gas

A

Cardiac troponins and CK-MB are measured.
An increase can indicate MI.
No increase can rule out an MI in patients with current chest pain and inconclusive ECG.

31
Q

Myoglobin and CK isoforms

A

Problem is its non specific. When absent, can rule out MI.
1-2 hours, peaks at 6 hours, back to normal in 2 days.

32
Q

CK-MB

A

2-6 hours rises
Peaks at 20 hours
Normal after 2-3 days.
“Early increase, sharp peak after 1 day and back to baseline at 2 days.”

33
Q

Troponin

A

Most specific
Peaks in 12-24 hours
Stays up for 7-10 days.
Most sensitive
“Early increase but the stay elevated longer than CK-MB.
cTnT stays longer elevated than cTnI.

34
Q

Liver injury leads to loss of function and to leakage of membrane
Liver function test examples
Ammonium

A

High
“Smoke some ammonium and you’ll get high”

35
Q

Liver injury leads to loss of function and to leakage of membrane
Liver function test examples
Albumin

A

Reduced
Al is a bum who is reduced to lowest levels

36
Q

Liver injury leads to loss of function and to leakage of membrane
Liver function test examples
Bilirubin

A

High
“Let’s get high with Billy and Rubin”

37
Q

Liver membrane integrity test

A

Alanine aminotransferase (ALT) - only found in cytoplasm. That’s where “Alan hangs out.”
Aspartate aminotransferase (AST) - In cytoplasm AND Mitochondria. Aspirating due to all the hard work in the mitochondria.

38
Q

Ratio of ALT/AST can indicate source of liver damage

High ALT/AST ratio is characteristic of…

A

Hepatic viral infection. (Hepatitis A, B, C, D, E)

39
Q

Ratio of ALT/AST can indicate source of liver damage

High AST/ALT ratio is characteristic of…

A

Hepatic alcohol damage.
The alcohol goes to damage mitochondria, so AST released.

40
Q

Bile duct obstruction
Extra-hepatic bile ducts are obstructed by

A

-Gallstones (cholesterol gallstones)
-Tumors (tumor in head of pancreas)

Gallstones and tumors are so “Extra”. But really a lot of both of them can happen and is not good.

41
Q

Bile duct obstruction
Inter-hepatic bile ducts can be irritated in…

A

Liver cirrhosis.

42
Q

Injury markers for obstructed bile ducts
Any obstruction in biliary.

A
  1. Alkaline Phosphatase (ALP)
  2. Gamma-glutamyl transferase (GGT)

AL Pacino is Getting GeriaTric. So his bile is obstructed.

43
Q

[…] is found in high concentration in cells of the bile canaliculi and biliary ducts. […] cleaves phosphatase from nucleotides and proteins which leads to the alkaline pH of bile.

A

Alkaline phosphatase (ALP)

AL Pacino starts to make alkaline pH of bile.

44
Q

[…] is bound to the plasma membrane of hepatocytes (liver cells) and is part of the hepatic […] cycle for glutathione (GSH) synthesis.

[…] increase in serum indicated injury in bile ducts and of the liver. It can result from gallstones, ethanol, or medical drugs.

A

Gamma-glutamyl Transferase (GGT)

Grandma is Getting geriaTric. So lots of gallstones and medical drugs. Can’t explain the alcohol though.

45
Q

Acute injury of this due to: Heavy alcohol intake (40%)
Gallstone blockage (40%)

Chronic due to: Cystic Fibrosis (CF), Hyperlipidemia, Years of ethanol abuse (alcohol)

A

Pancreatitis

46
Q

Acute pancreatitis indicated by increased serum levels of…

A

Alpha-amylase and pancreatic lipase

47
Q

Ethanol as pancreatitis

A

Serum lipase/amylase ratio greater than 2

48
Q

Gallstones as marker for pancreatitis

A

Blockage: increase of serum amylase, lipase, ALP and GGT

49
Q

Chronic pancreatitis

A

Can show less enzyme increase in serum due to less synthesis inside the pancreas.

50
Q

Alcohol related damage of liver

A

Serum: AST/ALT ratio larger than 2
GGT and ALP (cirrhosis)

51
Q

Alcohol related damage of pancreas

A

Serum: Lipase/amylase ratio larger than 2
GGT

52
Q

[…] Found in bone, bile ducts, placenta, and intestine

A

Alkaline phosphatase
ALP in bones creases an alkaline pH for calcium deposition onto collagen.
Natural rise of ALP (alkaline phosphatase occurs in serum during bone growth and healing of fractures and during pregnancy.

53
Q

Abnormal increase of Alkaline phosphatase (ALP) in serum happens in […] this disease or […] this.

A

Happens in Paget disease or bone tumors.

AL Pacino has PAGET

Note: high serum ALP is also found in bile duct obstruction but is then combined with high GGT.

54
Q

Prostate cancer

A

Prostate specific antigen test
(Instead of test for acid phosphatase)

55
Q

Liver cancer

A

Alpha-fetoprotein (AFP):
This protein is normally synthesized in the fetal liver (instead of albumin).
In adults it can indicate liver cancer.

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