Sertoli & Leydig cells
NADPH
CYP11A1/P450 catalyses oxidation of cholesterol by using electrons from what?
Gonadotropin releasing hormone GnRH
Hormone from hypothalamus that promotes secretion of follicle-stimulating hormone (FSH) and luteinizing hormone (LH)
Mullerian inhibiting substance MIS
a hormone released by sertoli cells that causes regression of the mullerian ducts (which go on to form female reproductive system) - important in sex determination
50-100ug/day
approx dihydrotestosterone (DHT) production rate
10-15ug/day
approx estradiol production rate
5mg/day
approximate testosterone production rate
tight junctions
by what are sertoli cells held together?
5a reductase = DHT, aromatase = estradiol
catalytic enzymes and products of testosterone conversion
aromatase cyp19
converts small amount of leydig cell derived testosterone to potent estradiol 17b (estrogen)
androgen response element
dimerisation and phosphorylation of DHT/Testosterone bound Androgen Receptor cuases formation of what?
glycolysis
due to the blood testis barrier, sertoli cells are responsible for providing substrates for what?
p450
enzyme system responsible of translocation of cholesterol and production of testosterone
5a reductase
enzyme that converts testosterone to DHT
proteases and protease inhibitors
glycoproteins secreted by sertoli cells involved in tissue remodelling during spermination and movement during spermatogenesis
at least 1
how many isoforms of the estrogen receptor (ER) are expressed on sperm cells?
cholesterol hydrolysis and expression of StAR
immediate effects of LH stimulating cAMP-PKA pathway in leydig cell
sertoli cell glut1 transporter -> metabolised to lactate -> sperm specific lactate transporter
journey of glucose in sertoli cell to germ cell
increased steroidogenic enzymes and LDL receptors
longer term effects of LH stimulating cAMP-PKA pathway in Leydig cell
secretion of ferric ions and synthesis of testicular transferrins
movement of iron through sertoli cells results in what?
growth and paracrine factors
number 1 function of sertoli cells is to provide what
LH stimulates cAMP-PKA pathway -> cholesterol translocation via StAR -> pregnenolone -> translocation to ER -> testosterone
pathway of testosterone production in leydig cell
inhibin
protein hormone secreted by sertoli cells, inhibits FSH secretion, helps regulate sperm production
constant / direct
relationship between sertoli cell number and germ cell number
DHT
required for masculinization of external genitalia, development of prostate gland and changes associated with puberty
their antigens stimulating autoimmunity
the blood-testis barrier isolates spermatocytes and spermatids from the immune system to prevent what?
transferrin, ceruloplasmin
transport/bioprotective proteins secreted by sertoli cells in high abundance
LH = interstitial/leydig cells, FSH = sertoli cells
upon what do each of the 2 hormones secreted by pituitary glands act?
negative feedback of LH release
upon what does circulating testosterone have an effect/regulate
glycoproteins
what are secreted by sertoli cells to help maintain biochemistry within system
transport, proteases & inhibitors, basement membrane, regulatory
what are the types of (functions of) glycoproteins that are secreted by the sertoli cells?
CYP11A1 / p450scc
what catalyses the conversion of cholesterol to pregnenolone via 3 oxidation reactions in the same site
diffusion of materials between cells
what do the tight junctions that hold sertoli cells together limit?
DHT binds with greater affinity
what is the difference between testosterone and DHT binding with Androgen Receptor?
can translocate into nucleus
what is the importance of the formation of the Androgen Response Element complex (ARE)?
lactate
what is the preferred substrate for glycolysis in primary spermatocytes?
allow movement of iron through
what is the role of transferrin receptors on sertoli cells
blood testis barrier
what isolates luminal fluid from the fluid bathing the cells in the basal compartment to protect sperm cells from immune attack (antibodies)
sertoli cells
what produces aromatase (CYP19)?
androgen binding protein
what protein do sertoli cells make and secrete
luminal
what sort of fluid is secreted by sertoli cells
regulatory
what type of glycoproteins secreted by sertoli cells are lowest in abundance
type 2
which of the 2 isoforms of 5a reductase is the most important
appear after puberty
why would spermatocytes and spermatids be recognised by the immune system as 'foreign' cells
