Spermatogenesis

ROLE OF SERTOLI CELLS IN SPERMATOGENESIS

Sertoli cells influence spermatogenesis by four ways. Sertoli cells:

  1. Support and nourish the germ cells
  2. Provide hormonal and other substances necessary for spermatogenesis
  3. Secrete androgen binding protein (ABP) which is essential for testosterone activity, particularly on spermatogenesis
  4. Release the sperms into lumen of semiferous tubules (spermination).

Spermatogenesis

ROLE OF HORMONES IN SPERMATOGENESIS

Spermatogenesis is influenced by many hormones which act either directly or indirectly. The hormones necessary for spermatogenesis are:

  1. Follicle stimulating hormone (FSH)
  2. Testosterone
  3. Estrogen
  4. Luteinizing hormone (LH)
  5. Growth hormone (GH)
  6. Inhibin
  7. Activin.

1. FSH

FSH is responsible for the initiation of spermatogenesis. It binds with Sertoli cells and spermatogonia and induces the proliferation of spermatogonia. It also stimulates formation of estrogen and androgen binding protein from Sertoli cells.

2. Testosterone

Testosterone is responsible for the sequence of remaining stages in spertmatogenesis. It is also responsible for maintenance of spermatogenesis. Testosterone activity is largely influenced by androgen binding protein.

3. Estrogen

It is formed from testosterone in Sertoli cells. It is necessary for spermeogenesis.

4. LH

LH is essential for the secretion of testosterone from Leydig cells.

5. GH

GH is essential for the general metabolic processes in testis. It is also necessary for proliferation of spermato¬gonia. In pituitary dwarfs, the spermatogenesis is severely affected.

6. Inhibin

Inhibin is a peptide belonging to transforming growth factor family. It is secreted by Sertoli cells. It is also secreted in females by granulosa cells of ovarian follicles. Its secretion is stimulated by FSH and inhibited by GnRH.

Inhibin plays an important role in the regulation of spermatogenesis by inhibiting FSH secretion through feedback mechanism. FSH secreted from anterior pituitary induces spermatogenesis by stimulating Sertoli cells. It also stimulates the secretion of inhibin from Sertoli cells. So, when the rate of spermatogenesis increases, there is simultaneous increase in inhibin secretion also. Inhibin in turn acts on anterior pituitary and inhibits secretion of FSH leading to decrease in the pace of spermatogenesis.

It is believed that inhibin also inhibits FSH secretion indirectly by inhibiting GnRH secretion from hypothalamus.

7. Activin

Recently the peptide called activin is also found to be secreted in gonads along with inhibin. The exact location of its secretion in testis is not known clearly. It is suggested that it is secreted by Leydig cells and Sertoli cells.

Activin has opposite actions of inhibin. It increases secretion of FSH and accelerates spermatogenesis.