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Phys Exam two > Steroid hormone receptors > Flashcards

Steroid hormone receptors Flashcards

1
Q

Steroid hormone receptors - Intracellular examples (8)

5 that are cholesterol derivatives, 3 that are not, what are they?

A

All receptors - androgen, estrogen, progesterone, glucocorticoid, mineralcorticoid,
Which are not cholesterol derivatives?
Vitamin D3, Retinoic Acid, Thyroid hormones

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2
Q

What are the steroid hormone receptor agonists derived from cholesterol?

A

progesterone, testosterone, estradiol, aldosterone, cortisol.

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3
Q

What are the steroid hormone receptor agonists NOT derived from cholesterol?

A

Vitamin D Cholecalciferol, Retinoic Acid, and thyroxine

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4
Q

What can change testosterone into the active form?

What is the active form called?

A

Enzyme a-5-reductase can change testosterone into Dihydrotestosterone or DHT

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5
Q

If you take a hydroxy group off of cortisol, what does it become?
What animals does this occur in?

A

Cortisol becomes corticosterone, seen in rodents, birds, amphibians

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6
Q

What turns cortisol into cortisone?

Is this active or inactive?

A

11BHSD, inactive

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7
Q

What are some examples of carrier proteins?

A

Vitamin D binding protein, Retinol binding protein, Thyroxine binding globulin, Sex hormone binding globulin, transcortine.

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8
Q

What is Thyroxine binding globulin binding for?

A

thyroid hormones

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9
Q

What is sex hormone binding globulin for?

A

steroid androgens and estrogens

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10
Q

What is transcortin for?

What does it have a low affinity for?

A

Cortisol

Low affinity for progesterone and aldosterone

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11
Q

What do all steroid hormone receptor structures contain?

A

ligand (hormone)-binding domain, DNA binding domain, and transcription-activating domain.

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12
Q

What solubility do steroid hormone receptors have and what do they act as, what do they extend?
Has a low affinity, high capacity for what?

A

All lipid soluble; act as circulating reservoir, extend 1/2 life of circulation
Low affinity, high capacity for albumin

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13
Q

What is the 1st step in hormone signaling?

A

Ligand synthesized, secreted, and enters circulation

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14
Q

What is the 2nd step in hormone signaling?

What does the ligand associate/dissociate from?

A

Associates with/dissociates from carrier(s) to have a relatively stable concentration of free ligand circulation, most bound, some free

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15
Q

What is the 3rd step in hormone signaling?

What occurs and how?

A

By diffusion, free ligand crosses vasculature cell layers, interstitial fluid and cell membrane to enter the cytosol (and nucleus)

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16
Q

What is the 4th step in hormone signaling?

A

Receptor binding and release of inhibitory protein

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17
Q

What is the 5th step in hormone signaling?

A

Access nucleus via nuclear pore and dimerize

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18
Q

What is the 6th step in hormone signaling?

A

Bind DNA at specific sites

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19
Q

What is the 7th step in hormone signaling?

A

Associate with co-factors and initiate transcription

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20
Q

What is the 8th step in hormone signaling?

A

RNAs leave nucleus via nuclear pore

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21
Q

In signaling mechanisms, ligands are located where, for how long? Bound to what?

A

Ligands in vasculature are bound to carrier proteins, which reduce renal excretion. Ligands in vascular circulation for hours until they are excreted (vascular reservoir).

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22
Q

Are ligands hydrophilic or hydrophobic?

What does this necessitate?

A

hydrophobic, necessitates carrier proteins in circulation

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23
Q

Free ligands have what solubility? This can allow them to do what?

A

They are lipid soluble and can exit circulation and enter cells by diffusion across lipid membranes

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24
Q

What do ligands bind to and activate?

A

Intracellular receptors

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25
Where is the activated hormone receptor complex? | What does it bind to?
It is in or enters the nucleus, dimerizes and binds to a specific sequence on DNA
26
What does the activated hormone receptor complex bind to? What does this initiate?
Binds to a specific DNA sequence which initiates transcription given that the appropriate set of transcription co-factors are present
27
What occurs after transcription initiation?
mRNA leaves the nucleus for translation into proteins
28
Where are intracellular receptors located?
Either in the cytosol or in the nucleus.
29
If a receptor is in the nucleus, what does is reside as?
inactive receptors on DNA
30
What does ligand binding activate and initiate?
Activates the receptor and initiates transcription (mRNA from DNA) given that transcription factors are present.
31
What are two exampled of cytosolic receptors?
Glucocorticoid receptor and mineralcorticoid (aldestorone) receptor
32
What are three example of nuclear receptors?
Thyroid hormone receptor, vitamin D3 receptor, and retinoid receptor
33
For signaling, cells must contain what components?
Cells must contain the receptor and some ancillary enzymes can be required.
34
What converts cortisol to cortisone?
11B hydroxysteroid dehydrogenase
35
What converts testosterone to dihidrotestosterone?
5a reductase
36
Is signaling vita intracellular receptors fast or slow?
slow; minutes to days for cellular and/or systemic effects
37
Carrier proteins present a reservoir for?? Are the diffusion paths for ligands short or long? Effect of signaling requires what? What does termination require, often what?
Carrier proteins present a reservoir for ligands buffering changes in free concentration; long diffusion paths for ligand; effect requires transcription and translation (potential subsequent metabolic steps). Termination requires excretion of hormone - often as bile after conjugation in liver
38
``` Mineralcorticoid Receptor Example - aldosterone Condition? Origin? Carrier Protein? Receptor? Effects? ```
``` Condition - decrease in blood pressure origin - adrenal cortex Carrier protein - albumin; transcortin Receptor - mineralcorticoid receptor Effects - Na+ and H2O retention/K+ excretion; maintenance or increase i n blood pressure ```
39
What is Renin? what is it released by and in response to what?
Renin is an enzyme that is released by the kidney into the blood stream in response to a drop in blood pressure
40
What reactions do renin catalyze?
The first two reactions that lead to the production of angiotension two. 1 - angiotensinogen > angiotensin 1 (renin) 2 - Angiotensin 1 > Angiotensin 2
41
What is Angiotensin two stimulate? Induces/increase? Enhance?
Stimulates aldosterone production and release from the adrenal cortex. Induces/increases vasoconstriction, enhances vasopressin (ADH) secretion
42
What stimulates Na+ and water retention by kidney, what does this cause?
Aldosterone and angiotensin 2, causes conservation of blood volume
43
What causes an increase in BP?
Vasoconstriction and the stable/increased blood volume.
44
What does Aldosterone cause? | Increased numbers of these iron transport proteins increases what?
Causes the translation and transcription of genes that code for an apical Na+ channel, an apical K+ channel and the basolateral Na+/K+ ATPase. Increased numbers of these ion transport proteins increases Na+ and water retention (and K+ excretion).
45
``` Thyroid hormone recepter - Thyroxine (T4) and Tri-iodo-thyronine (T3): Condition? Origin? Carrier Proteins? Receptor? Effects? ```
Condition - cold and/or stress Origin - thyroid gland synthesizes and stores the prohormone thyroxine (T4) from which one iodine is removed to generate the hormone T3. Carrier proteins - thyroxine-binding prealbumin and thyroxine-binding globulin. Receptor - thyroid hormone receptor. Effects - General increase in metabolism; increase O2 consumption and ventilation; thermogenesis; mobilization of fat and protein
46
Thyroid hormone pathway: | What causes the hypothalamus to release TRH? What does this reach?
Cold and stress causes the hypothalamus to release TRH which reaches the pituitary gland via the blood stream
47
What does TRH cause the release of? | What does TSH Stimulate?
TRH causes release of TSH from cells in pituitary; TSH stimulates the thyroid gland to release thyroid hormone consisting mostly of T4 with some T3, the biologically active hormone
48
What is T4 converted to and by what? Where is the conversion factor located?
Converted by de-iodinases to T3; De-iodinases are located primarily in liver and kidney
49
What does T3 do?
Mediates a general increase in metabolism; increased O2 consumption and ventilation. Thermogenesis, mobilization of fat and protein.
50
What does T4 do?
Exerts negative feedback by inhibiting TSH release from the pituitary gland
51
Feline hyperthyroidism presentation -
Weight loss (despite a good appetite), rapid heart rate (hyperexcitabilitiy), vomiting/diarrhea, and poor hair coat
52
Feline hyperthyroidism diagnosis | Most common _____ disorder in older cats.
rule out other diseases; determination of plasma levels of T4 most common endocrine disorder in older cats?
53
Suspected causes of feline hyperthyroidism
cats live longer, exposure to chemicals
54
Feline hyperthyroidism Etiology
most often causes by thyroid adenoma; only 2% of affected cats are diagnosed with thyroid adenocarcinoma; one or both lobes may be involved
55
Feline hyperthyroidism treatment
Methimazole (Tapazol) - inhibits T3/T4 production, surgical removal of thyroid gland, radio-iodine treatment with 131I; I emits B-particles that destroy tissue within 1 mm and has a 1/2 life of 8 days.
56
Most ligands are derivatives of what?
cholesterol
57
All steroid hormone receptors are _____, some _____
intracellular receptors, some nuclear
58
Ligands associate with what? Where
with carrier proteins in circulation; accounts for reservoir and for time course of effect
59
What are the three critical domains of receptors?
hormone binding; DNA binding; transcription activating
60
Steroid hormone receptors have typical t interactions with what? What is pathway activity modulated by?
co activators and repressors; pathway activity modulated by negative feedback loops

Phys Exam two (13 decks)

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