Role of Inhibins as an Intragonadal Modulator

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Role of Inhibins as an Intragonadal Modulator

• Teresa R Petrino and Y-W Peter Lin
• School of Natural and Health Sciences, Barry
  University, Miami Shores, Florida

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Pituitary
Gonadotropins
LH FSH
Ovary
Steroids
Granulosa cell
T, E, P4
Gonadal peptides
Inhibin Activin Follistatin
Oocyte
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HYPOTHESIS
Inhibin may also function as an
autocrine/paracrine regulator in the ovary

• Endocrine (Long distance action)
• Paracrine (Local, acts on adjacent cell)
• Autocrine (Local, acts on the same cell)

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Effect of Inhibin on
Gonadotropin-induced steroid production by the
granulosa cells. (autocrine effect)
Steroid-induced oocyte maturation. (paracrine
effect)
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Fundulus heteroclitus ovary
40 x
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Rana pipiens
Ovarian follicles (1.5 mm in diameter)
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In vitro Culture of Ovarian Follicle
Treatments pituitary extracts (source of
Gonadotropins) Steroids (Progesterone, P4) (
DHP) inhibin (porcine)
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Response
Steroidogenesis Steroid levels measured by
Radioimmunoassay (RIA) Amphibian
progesterone Fish 17alpha,20beta-dihydro-
4-pregnene-3-one (DHP) Oocyte Maturation
reinitiation of meiosis or GVBD
GV (Prophase I)
Metaphase II
100x
GVBD
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Inhibin effects on gonadotropin-induced P4 and
GVBD on Rana Ovarian follicles
FPH 0.01 Pit. Eq./ml 24 hr culture
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Inhibin effects on gonadotropin-induced DHP and
GVBD on Fundulus Ovarian follicles
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Inhibin effects on steroid-induced GVBD
Rana
Fish
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Effects of inhibin on denuded oocytes
Denuded Oocyte oocyte without the surrounding
granulosa cells, theca and surface epithelium
Fish
Rana
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CONCLUSIONS

• Inhibin may serve as a paracrine/autocrine
  regulator of ovarian functions in both amphibian
  and fish species.
• Inhibin blocked steroid production in Rana
  (autocrine effect) but did not inhibit DHP in
  fish, suggesting that the inhibin effect is
  species specific.
• Inhibin may act as a paracrine modulator of
  oocyte maturation because its effect was dose
  dependent, not permanent or deleterious.
• Inhibin appears to act directly on the oocyte to
  cause inhibition or delay of the reinitiation of
  meiosis.

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Acknowledgements

• Research supported by NIH-MBRS SCORE Grant
  GM45455-08
• Tericka Smith supported by NIH-MARC USTAR Grant
  GM08021-17

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Questions