Endo: Hormones/Receptors

Question 1

In the endocrine system, hormones are released into _______________ and act on _________ cells

Answer 1

In the endocrine system, hormones are released into the blood and act on distant cells

Question 2

Compare paracrine, autocrine, and endocrine signaling

(released into…, target cell)

Answer 2

• Paracrine: effector released into extracellular space (acts on nearby cell)
• Autocrine: effector released into extracellular space (target is itself)
• Endocrine: effector released into blood (acts on distant cell)

Question 3

Is a chemical inherently endocrine, autocrine, or paracrine signaling?

Answer 3

NO. One chemical can act as a hormone, neurotransmitter, etc.

Whether a molecule is endocrine, autocrine, or paracrine depends on how it gets to the target cell

Question 4

How are water soluble hormones stored/released?

Why?

Answer 4

• Water soluble hormones are stored in vesicles
• Increased intracellular Calcium causes fusion of vesicles and release of hormone
  
  • aka Calcium-dependent exocytosis
• This system is used because water-soluble hormones can’t easily cross the cell membrane to get out into the blood

Question 5

What 2 kinds of hormones are water soluble?

Answer 5

Protein/peptide hormones

catecholamines

Question 6

How are steroid hormones stored/released?

Answer 6

• Steroid hormones have minimal storage b/c they are lipids (can’t hang out in cytoplasm)
• Steroid hormones diffuse across cell membrane to reach blood stream

Question 7

Steroid hormones are ____philic and derivatives of __________

Answer 7

Steroid hormones are lipophilic and derivatives of cholesterol

Question 8

Compare how steroid and water-soluble hormones travel through blood stream

How does this affect their half life?

Answer 8

• Water soluble hormones float freely in blood
  
  • Protein/peptide hormones thus have shorter half life b/c exposed to proteases
• Steroid hormones are bound to proteins in blood
  
  • Longer half life

Question 9

Which is more relevant: total hormone level or free hormone level?

Answer 9

Even though the majority of steroid hormones exist bound to protein, only the free hormone has a physiologic effect

So, the amount of free hormone is what we care about

Question 10

Water soluble hormones bind to __________receptors.

Name the 3 receptor types

Answer 10

• Water soluble hormones bind to cell surface receptors
• Receptors can be
  
  • GPCR’s
  • Cytokine receptor family
  • EGR-R

Question 11

What is the effect of the 3 different GPCR’s?

Answer 11

• Gs -> activates adenylate cyclase -> increases cAMP
• Gi -> inhibits adenylate cyclase -> decreases cAMP
• Gq -> activates PLC -> increases IP3, DAG

Question 12

What 2 water-soluble hormones use cytokine receptors?

What is the effect of cytokine receptors?

Answer 12

• Cytokine receptors used by GH, PRL
• Receptor binding -> Activates JAK (a kinase) -> STAT signaling -> increases transcription

Question 13

Name one hormone that uses EGF-Receptors

What is the effect of activating EGF-Receptors?

Answer 13

• Insulin uses EGF-R
• EGF-R activates its inherent tyrosine kinase activity and dimerizes

Question 14

What happens when a steroid hormone reaches its target cell (4)?

Answer 14

1. Steroid hormone diffuses across cell membrane
2. Steroid hormone binds to receptor in cytoplasm
3. Steroid hormone/receptor complex moves into nucleus
4. Steroid hormone alters transcription

Question 15

Is the effect of steroid hormones long-term or short-term?

What about water soluble hormones?

Answer 15

• Steroid hormones exert long-term effects by altering transcription
• Water soluble hormones exert short-terms effects by activating ready pathways

Question 16

Compare bioassay and immunoassay

Answer 16

• Both are used to measure protein hormone levels
• Bioassay measures activity of hormone as a surrogate for how much hormone is present
• Immunoassay directly measures amount of hormone present, but doesn’t assess functionality

Question 17

How do we measure the level of steroid hormones?

Answer 17

Because so much of the hormone is bound, it is difficult to measure hormone directly.

So, we measure the amount of a downstream hormone that responds to our hormone of interest