Inside this axis the most important role is taken by the Sertoli cells, and FHS hormones and inhibine and activine hormones.
Sertoli Cells and FSH
The connection between Sertoli cells and FSH is one of the most important regulatory elements inside male physiology. Just like LH, FSH is released by the pituitary gland as a response to GnRH action.
LH and FSH are extremely important in human spermatogenesis. LH has the function of stimulating Leyding to produce testosterone.
Sertoli cells physiologic role and their connection with pituitary gland hormones are very complex. The main steps of this process can be summed as it follows:
1. FSH is bind to the Sertoli membrane specific receptors and it modifies adenylate- cyclase activity.
2. The intracellular cAMP (cyclic adenosine monophosphate) level increases due FSH binding. Phosphodiesterase governs cAMP and at its turn it is influenced by the calcium dependent calmoduline.
3. Elevated cAMP stimulates a cAMP dependent protein-kinaza and phosphorylase Sertoli cells by regulating the citoplasmatic phosphokinase inhibitors, PKI.
4. As a result of the chemical reactions described above, unique in Sertoli cells, the synthesis and secretion of chemical high molecular mass components emerges. Those substances have an important role in local spermatogenesis paracrine regulation. Other chemical products, like inhibine, are involved in systemic modulation.
5. Once initiated, many of the FSH mediated phenomena are maintained by testosterone.
6. In this physiologic process, germinal cells, testicular mioides and Leyding cells have a very important role.
Inhibine is a polypeptide secreted by Sertoli cells as a chemical response to FSH release, which acts as a negative-feedback on the pituitary gland in order to maintain FSH functional level therefore it has a regulation function within the spermatogenesis-hypophysis axis.
Spermatogenesis Paracrine Regulation
Asides from the distant regulation with soluble hormones, through the hypophysis-Sertoli cells and hypophysis-Leyding cells axis, there is a local paracrine regulation between the different cells inside the testicle: Sertoli cells – germinal cells, Sertoli cells – peritubular cells, Sertoli cells – Leyding cells, Leyding cells – peritubular cells, etc.
The paracrine process of regulation plays an important part in maintaining and coordinating testicular cells’ normal activity; therefore it is also very important in the process of spermatogenesis, but, in spite of many years of scientific research the paracrine mechanism of infertility hasn’t been fully understood.