Adrenal Catecholamines Flashcards Preview

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Flashcards in Adrenal Catecholamines Deck (37):
1

What stain turns chromaffin cells yellow?

Chromium treatment

2

What are chromaffin cells thought of in terms of pre or post ganglionic nerves?

Think of them as post-ganglionic sympathetic neurons considering their contents

3

What do chromaffin granules contain?

Chromogranin A (tumor marker)
Chromogranin B (tumor marker)
ATP
Neuropeptide Y
Enkephalins
Adrenomedullin

4

How are catecholamines concentrated?

By 4:1 binding with an ATP molecule (proton pumps them in)

5

What is the vesicular proton pump needed for?

Catecholamine concentration in chromaffin granules

6

What is Adrenomedullin?

It is a marker for catecholamine release; increased would mean pheochromocytoma

7

What is the pathway for formation of the catecholamines?

Phenylalanine-> Tyrosine-> Dopa-> Dopamine-> Norepinephrine-> Epinephrine

8

What step does the catecholamine synthesis usually begin?

Tyrosine

9

Rate limiting step in normal catecholamine synthesis?

Tyrosine to Dopa Tyrosine hydroxylase

10

What enzyme is needed for phenylalanine to tyrosine formation?

Phenylalanine hydroxylase

11

What enzyme is needed for tyrosine to dopa formation?

Tyrosine hydroxylase

12

What enzyme is needed for dopa to dopamine formation?

L-Aromatic amino acid decarboxylase

13

What enzyme is needed for dopamine to norepinephrine formation?

Dopamine-Beta-hydroxylase

14

What enzyme is needed for norepinephrine to epinephrine formation?

PNMT

15

What is the rate limiting step in pheochromocytoma patients?

Norepinephrine to epinephrine formation (PNMT)

16

What controls the action of PNMT?

Glucocorticoid stimulation

17

Normal persons epinephrine to norepinephrine ratio?

4:1

18

Pheochromocytoma patient epinephrine to norepinephrine?

1:5

19

Where is the only place that epinephrine is synthesized?

Adrenal medulla

20

What inhibits tyrosine hydroxylase?

Alpha-methyl tyrosine

21

What inhibits vesicular monoamine transport?

Cocaine
Guanethidine
Selective norepinephrine reuptake inhibitors
Tricyclic antidepressants

22

What effect do monoamine oxidase inhibitors have?

Inhibit the breakdown of catecholamines

23

What effect do COMT inhibitors have?

Inhibit breakdown of catecholamines

24

What two enzymes are needed for breakdown of catecholamines?

COMT
MAO

25

What do you use alpha-methyl tyrosine to treat?

Pheochromocytoma inoperable one

26

What are the side effects of alpha-methyl tyrosine?

Cystalluria (renal damage)
Sleepiness
Parkinson's syndrome (decreased dopamine)

27

What are the two breakdown pathways of norepinephrine?

Norepinephrine to Normetanephrine via COMT Normetanephrine to Vanillylmandelic acid via MAO

Norepinephrine to Dihydroxymandelic acid via MAO Dihydroxymandelic acid to Vanillylmandelic acid via COMT

28

What are the two breakdown pathways of epinephrine?

Epinephrine to Metanephrine via COMT Metanephrine to Vanillylmandelic acid via MAO

Epinephrine to Dihydroxymandelic acid via MAO Dihydroxymandelic acid to Vanillylmandelic acid via COMT

29

What test has high specificity for Pheochromocytoma?

Plasma Metanephrine levels

30

Why are metanephrine levels tested and not Normetanephrine for pheochromocytoma?

Because only the adrenal medulla forms epinephrine and a pheochromocytoma acts as that; the periphery can increase norepinephrine levels

31

What test has the greatest sensitivity to pheochromocytoma?

24 hour urine measurements of epinephrine, norepinephrine and VMA

32

What is given in imaging studies to locate the pheochromocytoma tumor?

Meta-iodobenzylguanidine

33

How is meta-iodobenzylguanidine uptaken?

Via neuronal uptake

34

What has a higher sensitivity and specificity but is often only used in PET scanners?

F DOPA

35

Where is meta-iodobenzylguanidine uptaken?

Pheochromocytoma
Moderate in liver, salivary glands, urine

36

What is the treatment of symptomatic pheochromocytoma?

Alpha-1-antagonist Prazosin + Beta blocker in preparation for surgery

37

What is the mechanistic treatment of pheochromocytoma?

Alpha-methyl tyrosine or Beta blocker + phenoxybenzamine (non-selective alpha blocker) or surgery