pack Flashcards
(43 cards)
What is the order of potency of Estrone, estradiol, and estraiol from most potent to least potent?
Potency
Estradiol> Estrone > Estriol
What is the order of potency of others, DHT, and testosterone from most potent to least potent?
Potency
DHT > Testosterone > others
Where is 5a-reductase found and what is its function?
Found in: peripheral tissues adipose, prostate and skin
Function: Converts Testosterone into 5a-Dihydrotestosterone
What intiates male growth in an embryo?
by sex-determining region of the Y chromosome (SRY gene).
What is the first thing that begins the development of the testis and from where does it develop?
The SRY transcription factor begin development of the testis - from medulla of primordial gonad.
What does testosterone stimulate the development of?
Testosterone stimulate development of epididymis, vas deferens, and seminal vesicle from Wolffian ducts.
What does DHT stimulate the development of?
DHT stimulate development of male external structures – prostate, penis, penile urethra and scrotum.
What would happen if there was an absence in the SRY gene?
Absence SRY gene, gonads develop into ovaries
What happens when there is a deficeny in 5a-reductase in an embryo?
Clinical Box
5α-reductase deficiency—inability to convert testosterone into DHT → normal male internal genitalia, ambiguous external genitalia until puberty (when ↑ testosterone levels cause masculinization)
What would be the consequence of fever on spermatogenesis and steroidogenesis?
Spermatogenesis: failure
Steroidogenesis: uneffected
What forms the blood-testis barrier?
The tight junctions between Sertoli cells form the blood–testis barrier
What is located between sertoli cells other than tight junctions?
dividing germ cells
What is spermiation and what does it require in order for it to take place?
It is: the detachment of mature spermatozoa from the Sertoli cell into the lumen.
Requires: conversion of plasminogen to plasmin.
What do sertoli cells synthesize that is related to iron?
large amounts of transferrin for sperm development
What two hormones do sertoli cells bind?
Testosterone and FSH
What is the mechanism of signaling that FSH uses with sertoli cells?
FSH receptors are linked to adenylyl cyclase via G protein which activate cAMP and PKA
What does FSH stimulate the synthesis of in sertoli cells?
androgen-binding protein [ABP], plasminogen activator, inhibin, follistatin, and activin
What conversion does FSH indirectly induce?
It induces aromatase that converts androgens to estrogens
Q: What receptors do Leydig cells have, what do they stimulate, and how do they stimulate it?
A: Leydig cells have LH receptors that stimulate steroidogenesis through the nuclear transcription factor SF-1, which activates genes encoding CYP enzymes.
What stimulates steroidogenesis in the fetus instead of LH?
human chorionic gonadotropin (HCG)
What is the signaling mechanism that LH receptors use to induce steroidogenesis?
cAMP
What other receptors do leydig cells have and what is their effect on them?
Estrogen receptors in Leydig cells reduce the proliferation and activity of these cells.
Q: What is the role of testosterone in Sertoli cells?
A: In Sertoli cells, testosterone acts as a precursor for estradiol production, modulating responses to LH.
What is the full signaling process that occurs in leydig cells after LH binds to its receptors to induce steroidogenesis?
Luteinizing hormone (LH) stimulate cAMP-PKA which activate cholesterol release from cellular stores.
Cholesterol enters mitochondria, via the steroidogenic acute regulatory protein (StAR), to form pregnenolone.
Pregnenolone is transported to the smooth ER for steroid synthesis.
Testosterone is the end-product, which diffuses into the extracellular fluid.
