Regulation of testicular function in the stallion: An

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Regulation of testicular function in the
stallion An intricate network of endocrine,
paracrine and autocrine systems Janet F.
Roser Presented by Tyler Andrews Malcolm
Delovio Shannon Huggins Reza Rezaei
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Histology and Morphology of the Testes By Tyler
Andrews
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Testes Histology and Morphology
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(No Transcript)
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Sertoli Cells
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Histology

• 1 - seminiferous tubule
• 2 - spermatogonia
• 3 - primary spermatocytes
• 4 - secondary spermatocytes
• 5 spermatids
• 6 - interstitial connective tissue
• 7- Leydig cells

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Roles of LH, FSH, and Prolactin in Testicular
Function By Malcolm Delovio
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Glycoproteins
Luteinizing Hormone (LH)

Produced by the gonadotropes of the Ant.
Pit. Follicle Stimulating Hormone (FSH)
a
a
ß
ß
96 A.A.
118 A.A.
149 A.A.
Prolactin (PRL) Produced by the mammatropes of
the Ant. Pit.
199 A.A.
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Roles of PRL in Testicular Function
In the breeding season HOWEVER did not
stimulate testosterone or estrogen production in
culture BUT
Rats - transcription of
the estrogen receptor Rat, ram, and boar -
control synthesis of LH receptors in the testes
- activates androgen
synthesis -
stimulates spermatogenesis
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Roles of LH in Testicular Function
LH
Leydig Cell
Cholesterol
Testosterone
Aromatase
Estrogen
Androstenedione aromatase Estrone Sulfate
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Roles of FSH in Testicular Function
FSH
Sertoli Cell
Testosterone
Estrogen
(Also, inhibin and activin)

• Testosterone along with FSH communicates to the
  Sertoli cells to initiate and
• maintain germ cell development
• The true role of FSH in the stallion is still
  unclear

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Roles of FSH in Testicular Function (cont.)

• Hamsters are also long day breeders
• - Testosterone maintains spermatogenesis
  without FSH
• - FSH is needed to restore full spermatogenesis
  when entering breeding season
• FSH in colts
• - Peaks at 40 weeks, remains elevated, and
  increases again around 83 weeks
• - Fluctuations in concentration occur but
  declined by 3.5 years of age
• - LH and testosterone levels increased up to 5
  years
• Conclusions
• - FSH needed for Sertoli cell development and
  proliferation
• - Testosterone needed for Sertoli cell
  differentiation and maturation
• - FSH not a big factor for final maturation and
  maintenance of spermatogenesis

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Endocrinology of Melatonin, Opiods, Inhibin, and
Activin in the Testis By Shannon Huggins
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Activin

• Paracrine function
• Primary source in the testes is Peritubular Myoid
  cells and acts in a paracrine fashion to promote
  Sertoli cell proliferation in early testicular
  development
• Determines ultimate testis size in adults
• Down regulation in KO mice causes smaller
  testicular size and reduced fertility
• Endocrine function
• Stimulates FSH release in pituitary
• Important in regulation of FSH-? synthesis

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Opioids

• Regulate seasonal fluctuations in GnRH and LH
  release
• Act on hypothalmus as to supress GnRH release
  during the winter months

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Melatonin

• Secreted from the Pineal gland during periods of
  darkness
• Seasonal regulator of reproductive function
• Changes in day length change duration of
  melatonin secretion
• Acts indirectly on the Hypothalmus to suppress
  GnRH

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Inhibin

• Produced primarily in the Sertoli cells
• Inhibin acts on the pituitary to suppress
  production and release of FSH
• Acts in a paracrine fashion to affect
  steroidogenesis in Leydig cells

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Roles of Androgens and Estrogens in the Testes
and Male Reproduction By Reza Rezaei
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Endocrine Regulation of Steroids
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Autocrine-Paracrine effects of Testosterone
? Blood-testis barrier function ? Meiosis
Postmeiosis development of germ cells ? Modulate
gene expression, proliferation and
differentiation of sertoli cells
? Inhibition of germ cell apoptosis ? Initiate
and maintain development of germ cells
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Paracrine-Autocrine effects of Estrogen
Androgen
Cytochrome P450 Aromatase
? Leydig cell maturation and development
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Roles of Steroid Hormones
Testosterone ? Initiation and development of
germ cell sertoli cell differentiation,
spermatogenesis and steroidogenesis ? Development
and function of accessory glands and corpulatory
organs ? Male sex characteristics and behavior
Estrogen ? Regulation of testicular cell
development and function, spermatogenesis and
steroidogenesis by inhibition of androgen
production through action in the leydig cell
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Thank You!