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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
Q

Where is the activated hormone receptor complex?

What does it bind to?

A

It is in or enters the nucleus, dimerizes and binds to a specific sequence on DNA

26
Q

What does the activated hormone receptor complex bind to? What does this initiate?

A

Binds to a specific DNA sequence which initiates transcription given that the appropriate set of transcription co-factors are present

27
Q

What occurs after transcription initiation?

A

mRNA leaves the nucleus for translation into proteins

28
Q

Where are intracellular receptors located?

A

Either in the cytosol or in the nucleus.

29
Q

If a receptor is in the nucleus, what does is reside as?

A

inactive receptors on DNA

30
Q

What does ligand binding activate and initiate?

A

Activates the receptor and initiates transcription (mRNA from DNA) given that transcription factors are present.

31
Q

What are two exampled of cytosolic receptors?

A

Glucocorticoid receptor and mineralcorticoid (aldestorone) receptor

32
Q

What are three example of nuclear receptors?

A

Thyroid hormone receptor, vitamin D3 receptor, and retinoid receptor

33
Q

For signaling, cells must contain what components?

A

Cells must contain the receptor and some ancillary enzymes can be required.

34
Q

What converts cortisol to cortisone?

A

11B hydroxysteroid dehydrogenase

35
Q

What converts testosterone to dihidrotestosterone?

A

5a reductase

36
Q

Is signaling vita intracellular receptors fast or slow?

A

slow; minutes to days for cellular and/or systemic effects

37
Q

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?

A

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
Q 
Mineralcorticoid Receptor Example - aldosterone
Condition?
Origin?
Carrier Protein?
Receptor?
Effects?
A 
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
Q

What is Renin? what is it released by and in response to what?

A

Renin is an enzyme that is released by the kidney into the blood stream in response to a drop in blood pressure

40
Q

What reactions do renin catalyze?

A

The first two reactions that lead to the production of angiotension two.
1 - angiotensinogen > angiotensin 1 (renin)
2 - Angiotensin 1 > Angiotensin 2

41
Q

What is Angiotensin two stimulate? Induces/increase? Enhance?

A

Stimulates aldosterone production and release from the adrenal cortex. Induces/increases vasoconstriction, enhances vasopressin (ADH) secretion

42
Q

What stimulates Na+ and water retention by kidney, what does this cause?

A

Aldosterone and angiotensin 2, causes conservation of blood volume

43
Q

What causes an increase in BP?

A

Vasoconstriction and the stable/increased blood volume.

44
Q

What does Aldosterone cause?

Increased numbers of these iron transport proteins increases what?

A

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
Q 
Thyroid hormone recepter - Thyroxine (T4) and Tri-iodo-thyronine (T3):
Condition?
Origin?
Carrier Proteins?
Receptor?
Effects?
A

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
Q

Thyroid hormone pathway:

What causes the hypothalamus to release TRH? What does this reach?

A

Cold and stress causes the hypothalamus to release TRH which reaches the pituitary gland via the blood stream

47
Q

What does TRH cause the release of?

What does TSH Stimulate?

A

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
Q

What is T4 converted to and by what? Where is the conversion factor located?

A

Converted by de-iodinases to T3; De-iodinases are located primarily in liver and kidney

49
Q

What does T3 do?

A

Mediates a general increase in metabolism; increased O2 consumption and ventilation. Thermogenesis, mobilization of fat and protein.

50
Q

What does T4 do?

A

Exerts negative feedback by inhibiting TSH release from the pituitary gland

51
Q

Feline hyperthyroidism presentation -

A

Weight loss (despite a good appetite), rapid heart rate (hyperexcitabilitiy), vomiting/diarrhea, and poor hair coat

52
Q

Feline hyperthyroidism diagnosis

Most common _____ disorder in older cats.

A

rule out other diseases; determination of plasma levels of T4
most common endocrine disorder in older cats?

53
Q

Suspected causes of feline hyperthyroidism

A

cats live longer, exposure to chemicals

54
Q

Feline hyperthyroidism Etiology

A

most often causes by thyroid adenoma; only 2% of affected cats are diagnosed with thyroid adenocarcinoma; one or both lobes may be involved

55
Q

Feline hyperthyroidism treatment

A

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
Q

Most ligands are derivatives of what?

A

cholesterol

57
Q

All steroid hormone receptors are _____, some _____

A

intracellular receptors, some nuclear

58
Q

Ligands associate with what? Where

A

with carrier proteins in circulation; accounts for reservoir and for time course of effect

59
Q

What are the three critical domains of receptors?

A

hormone binding; DNA binding; transcription activating

60
Q

Steroid hormone receptors have typical t interactions with what? What is pathway activity modulated by?

A

co activators and repressors; pathway activity modulated by negative feedback loops

Phys Exam two (13 decks)

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