Mineralocorticoids and Aldosterone Flashcards
What are the three layers of the adrenal cortex?
Zona glomerulosa
Zona fasciculata
Zona reticularis
What does the zona glomerulosa do?
Produces mineralocorticoids (aldosterone)
What does the zona fasciculata do?
Produces glucocorticoids (cortisol) and androgens
What does the zona reticularis do?
Produces androgens
Specialized to secrete Dihydroepiandrosterone
What does the adrenal medulla do?
Epinephrine
Small amount of norepinephrine
Largest region of the cortex?
Zona fasciculata
Key enzyme in the zona glomerulosa needed for mineralocorticoids?
21-hydroxylase enzyme
Key enzyme in the zona fasciculata needed for cortisol?
21-hydroxylase
11-Beta-hydroxylase
What is the common step to formation of all the steroids?
StAR needed for cholesterol to produce Pregnenolone
Most common abnormalities to form adrenal gland dysfunction?
21-hydroxylase
11-Beta-hydroxylase
What is the first step in steroid synthesis?
Get cholesterol into the mitochondria
What transports cholesterol into the mitochondria?
StAR protein
What generates Pregnenolone from cholesterol?
Cholesterol side-chain cleavage enzyme
GFR mnemonic:
G: Salt (mineralocorticoids)
F: Sugar (glucocorticoids)
R: Sex (androgens)
What does ACTH stimulate production of?
Both cortisol and adrenal androgens
What is the feedback for ACTH inhibition?
Cortisol only
No androgen feedback to inhibit ACTH
What receptor does ACTH stimulate?
MC2R (melanocortin-2 receptor)
What is the primary mediator of aldosterone release?
A-II; less so by ACTH and K+ levels
Three actions of aldosterone on the kidneys:
- ) Sodium and therefore passive water reabsorption
- ) Potassium absorption by the principal cells of the cortical CT
- ) Active secretion of protons via proton ATPases in lumenal membrane of IC of CT
Three major pathways regulating the secretion of renin by granular cells at the JGA:
- ) Renal baroreceptors: decreased perfusion = increased renin
- ) Macula densa: decreased Na/Cl ions in DCT = increased renin
- ) Sympathetic nervous system: increased activity increased renin release via beta receptors
How does A-II cause aldosterone release?
A-II binding to AT1 receptor causing IP3 binding to IP3R and release of intracellular Ca2+
What is the indirect method by which aldosterone inhibits ACTH release?
Systems effects of regulating blood volume and blood pressure leads to inhibition of ACTH release
What do principle cells express?
11beta-HSD2
What does 11beta-HSD2 cause?
Breaks down glucocorticoids so that they do not have as high of an affinity to the same receptors as mineralocorticoid receptors
