Exam - Endocrine Regulation of Repro Flashcards
how many major types of GNRH
3 (1 in mammals)
what are present in all vertebrates
decapeptides
how is GnRH released
in a pulsatile manner in the median eminence
how does GnRH travel
via portal blood system to the anterior pituitary
what happens in the hypothalamus with GnRH
GnRH neurons receive info about internal and external status
what are GnRH receptors
G-protein coupled receptors
how many GnRH receptors do most species possess
at least 2
what are the speculated exceptions for species that possess amount ofGnRH receptors
primates
rodents
what can GnRH stimulate upon binding to receptors
both Gaq and Gas
what happens in the pituitary when GnRH binds to receptor
leads to the synthesis and release of gonadotropins (LH and FSH)
where else are GnRH receptors present
ovary
prostate
placenta
what are glycoprotein hormones composed of
2 subunits:
common alpha
specific beta
what are the 2 specific hormone subunits in glycoprotein hormones
LHB
FSHB
what are LH and FSH produced by in most mammals
the same pituitary cells (gonadotropes)
what are LH and FSH produced by in avian
different cell types
what is differential regulation of LH and FSH based on
GnRH pulse frequency
what is the limiting factor of LH and FSH
B SU
what level is LH and FSH control
gene transcription level
how are LH and FSH sotred
stored in vesicles until signal (GnRH) is received, then they are secreted
what does the LH receptor activate
Gas - increases in cAMP
what does the LH receptor bind
both LH and hCG
what is hCG
placental source of gonadotropin
what is the FSH receptor
also a G-protein coupled receptor signalling via Gas
what are inhibin and activin
glycoproteins composed of 2 subunits
what is inhibin produced by
Sertoli cells in males
granulosa cells in females
what does inhibin inhibit
FSH
what does activin stimulate
FSH`
what do inhibin and activin mainly act in conjunction with
GnRH
what are gonadal (sex) steroids derived from
stepwise conversion of cholesterol - lipophilic with nuclear (intracellular) receptor
what does the type of gonadal steroid depend on
the presence of specific enzyme substrate in the cell
what type of steroid is estradiol-17B
potent
what are sex steroid receptors
NHR - effect on gene expression
what has recently been discovered about sex steroid receptors
non-genomic rapid effects discovered
why do steroids have multiple target organs
steroids diffuse in virtually any cell of the body and receptors are widely distributed
what receptor does testosterone use
the androgen receptor
what are the 2 receptor types that estrogens have
ERa
ERB
what do receptors require
coactivators/regulatory molecule to mediate their actions on target gene promoters
what is the main difference between ERa and ERB
location/presence (cell type)
Era stimulates transcription
ERB inhibits transcription
what does the effect of drugs depend on
ability to bind and activate ERa or ERB
what is the key link
kisspeptin
when was kisspeptin discovered
early 1999/2000
what was kisspeptin originally cloned as
an anti-metastasis agent
what is kisspeptin’s receptor
GPR54
where has kisspeptin’s receptor been localized
in the hypothalamus on GnRH neurons
what has happened with kisspeptins over the last 25 years
kisspeptins have been studied in their role in regulating puberty and modulating the negative feedback of steroid in males and females
what is the missing link
GnRH neurons do not express ERs but kisspeptin neurons do
