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75 Cards in this Set

  • Front
  • Back
Conversion of the C27 cholesterol ring involves the rate-limiting, irreversible cleavage of
the 6-C residue from cholesterol
Steroids with 21 C atoms are known as
produced from progesterone in the zona glomerulosa
an esterogen, produced in the ovary responsible for 2ndary sex characteristics
Principal mineralcorticoid
principle glucocorticoid
symthesized from progesterone in zona fasciculata
all steroid hormones exert action by passing through plasma membrane and binding to
intracellular receptors
specific nucleotide sequences bing to hormone-receptor complexes
Hormone response elements HREs
Leutinizing hormone stimulates sythensis of
ACTH hormone stimulates sythensis of
FSH hormone stimulates sythensis of
Angiotensin I and II stimulates sythensis of
committed and reat-limiting step of steroid synthesis
cleavage of a 6-carbon group from cholesterol
the NZ system catalysing the 6-C group is the
P450 linked side cleavage NZ
P450 sc or desmolase is found in the __________ of steroid producing cells
mitochondria (not in significant quantities in other cells)
desmolase consists of cyt P450 and
adrenadoxin (a P450 reductant)
1) cAMP stimulates PKS - leads to
phosphorylation of cholesterol-ester esterase
↑ concentrations of cholesterol
2) gene for desmolase contain cAMP regulated reg. element CRE binds cAMP and ____
↑ levels of desmolase RNA transcription
↑ levels of NZ
Cholesterol is a NEGATIVE feedback regulator of HMG CoA reductase activity. When cytosolic cholesterol is depleted ____
de novo synthesis of cholesterol is stimulated
HMG CoA reductase is freed of restraints
Subsequent to desmolase activity, prenenolone ____
moves to cytosol - further processed
hydroxulases involved in synthesis of steroid hormones are members of
Cyt P450 Nzs
Indictes site of hydroxylation
eg. P450c17
Adrenal cortex produces 3 major classes of steroid hormones
Adrenal insufficiency is know as
Addison's disease
Zona glomerulosa cells lack P450c17 that converst pregnenolone and
progesterone to C17 hydroxylated analogs
Zona glomerulosa
pathways to glucocorticoids (___) and andgrogens (____) are blocked
deoxycortisol and cortisol
DHEA and androstenedione
Zona glomerulosa
unique - contain NZ that converts corticosteron to
aldosterone - principal mineralcorticoid
The NZ P450c18 or 18a-hydeoxylase is also called
aldosterone synthase
Zona Fasciculata and Zona reticularis lack P450c18 and cannot convert corticosterone to
Zona Fasciculata and Zona reticularis contain P450c17 and produce
cortisol - the major glucocorticoid
Zona Fasciculata and Zona reticularis contain C17, 20 lyase whose activity is resp. for producing
the androgens
P450ssc is converted to androgens or
11-deocycortisol and
11-deoxycorticosterone by NZs in the
Endoplasmic reticulum
after conversion - renter the ______ and NZs convert to
ACTH of hypothalamus
regulates hormone production of
Zona Fasciculata
Zona Reticularis
ACTH receptors in the plasma membrane activates
aednylate cyclase → 2nd messenger cAMP
ACTH - clssic feedback loop CRH
Mineralcorticoid secretion from the _____
zona glomerulosa
Kidney protease acts on → Angoistensinogen from liver → stim zona glom cells by binding plasma membrane receptor coupled to
Phospholipase C
This angiotensin II and III bind to their receptors → leads to activation of _____ and elevated ______
activates PKC
↑ intracellular Ca++
↑ P450 SSC
↑ aldosterone
In the kidney aldosterone regulates Na+ retention by stimulating gene expression of
mRNA for Na+/K+ ATPase responsible for re-accumulation of Na+ from urine
Drugs widely used to lower blood pressure
ACE inhibitors
ACE inhibits compete with
NZ that convert angiotensis I to active angiotensin II and III
Feedback loop of ACE imhibitors os closed by
K+ - potent stimulator of aldosterone
K+ increases aldosterone secretion by depolarizing the plasma membrane of _____ opening voltage gated
Zona glomerusola cells - Ca++ channel
↑ cytoplasmic Ca++and stimulation of Ca++ dep processes
Low levels of of circulating sex hormones reduce the _____ and lead to elevation of FSH and LH
feedback inhibition of GnRH synthsis (long loop)
FSH and LH bind to gonad tissue and stimulate P450SSC activity resulting in sex hormone production via
PKA mediated pathways
Andenylate cyclase activation is coupled to the binding of
LH to plasma membrane receptors
testes and ovaries contain an additional NZ ______ that enables androgens to be converted to
In males LH binds to ___ cells and stimulates _____
Testosterone is secreted into the plasma and also carried in the ____ cells by ________
Androgen Binding proein (ABP)
In Sertoli cells the D4 double bond of testosterone reduced producing
dihydrotestosterone (DHT)
testosterone and DHT are carried in the plasma and delivered to tissues by
gonadal-steroid binding globulin (GBG)
In some tissues testosterone can be converted to DHT - the most ______
potent of the male steroid hormone
(testosterone sometimes considered a prohormone)
Testosterone can also be produced int the ____ cells, but it is regulated by _____
FSH also stimulates Sertoli cells to produce ____ which transports Testosterone and DHT from ____ to ______
Leydig cells to sites of
There testosterone acts to stimulate
sperm development and
proten synthesis
In females, LH binds to ______ where is stimulates synth of ______ by the usual
thecal cells of the ovary
androstenedione and testosterone
cAMP and PKA reg pathways
Aromatase is responsible for the final ____
conversion of into estrogen
complex NZ in ______ found in the
ovary and other tissues
its hydroxylations and dehydrations culminate in the ____
aromatization of the A ring of androgens
Synthesis of testosterone and androstenedione occurs from _______
Aromatase activity is also found in ______ but the activity is stimulated by
granulosa cells
Normally thecal cell androgens are produced in response to ______ and diffuse to _________
granulosa cells
Granulosa cell aromatase converts androgens to ____-
As granulosa cells mature they develop a large number of _____ receptors in the _____ ↑ wuantity of estrogen produced
plasma membrane
granulosa cell estrogens are largely secreted into
follicular fluid
Thecal cell estrogens are secreted into the ____ where they are delivered to taget tissues by
GBG (also used to transport testosterone
The binding of hormone, and/or phosphorylation of receptor Heat Schok Proteins (HSP) initiate movemnt of
nuclear receptor to the nucleus
HREs are on the DNA in the
promoter egion
The hormone receptor complex often binds as homodimer to _____ and bends the DNA at the _______
palindromically oriented HREs
site of binding
Disaggregation - hormone level falls - movement of receptor back to _____ where ____ can bind
The steroid and thyroid family of receptors have three distinct domains
a ligand binding region
a DNA binding domain and
a transcriptional reg domain
Binding of thyroid hormone to its receptor results in
release of rceptor from the DNA
Binding of glucocorticoid leads to _____ of ligand-binding receptor from cytosol to ____
The receptors for the retinoids are ID as _____ and have three subtypes