401-407. Corticosteroid Production and Regulation Flashcards
What are steroid hormones derived from?
Enzymatic modification of cholesterol
Where are enzymes which produce steroid hormones from cholesterol stored?
In the mitochondria and smooth ER
What class of enzymes are primarily responsible for the production of steroid hormones?
Cytochrome P450 enzymes
What is 11 beta-HSD responsible for and why is this important?
Converts active cortisol to inactive corticosterone in selected tissues, such as the kidney.
This allows mineralcorticoids to bind to receptors to carry out their functions as otherwise cortisol would take up most of the MRs - cortisol can bind to MRs and are much greater in concentration
List the actions of cortisol, both positive and negative
Stimulates gluconeogenesis
Allows for greater glycagon action
Increases lipolysis
Acts as an insulin antagonist
Increases skeletal muscle protein and reduces bone formation
Negative effects:
- on memory, learning and mood
- Suppresses immune system
What is the rapid action of ACTH?
Stimulation of cholesterol delivery to the mitochondria
What is the long term action of ACTH?
Increased transcription of genes coding for steroidogenic enzymes
What type of receptor is the ACTH (MC2) receptor?
G-protein coupled receptor
What type of receptor does angiotensin II bind to?
G-protein coupled receptor
What does binding of angiotensin II to it’s receptor activate?
Phospholipase C
What is phospholipase C responsible for?
The hydrolysis of PIP2 into second messengers IP3 and DAG
What causes the release of stored Ca+ as a result of angiotensin II?
IP3
What are responsible for the stimulation of StAR transcription and cholesterol uptake into mitochondria?
Ca2+ - calmodulin dependent kinases (CaMKs)
What converts angiotensinogen into angiotensin I?
Renin
What converts angiotensin I into angiotensin II?
Angiotensin Converting Enzyme (ACE)
