Follicle stimulating hormone, the Sertoli cell, and spermatogenesis

Regardless of the question of the hormonal specificity of the androgen binding protein (ABP) response, it is clear that FSH has a major effect upon the Sertoli cell of the testis. This gonadotropin binds to membrane receptors which couple to adenylate cyclase and results in an increased intracellular accumulation of cAMP. This cAMP activates a specific form of cytoplasmic protein kinase, which results in increased phosphorylation of a variety of proteins. Whether or not ABP can be used to assess the specific response of a Sertoli cell to FSH and whether these events are coupled with cyclic nucleotide mediated events are still uncertain. It is clear that testosterone will also rapidly increase the level of ABP. Moreover, NIH FSH preparations, which are known to be contaminated with LH, increase the testicular concentration of testosterone. On the other hand, LER 1577, a human FSH preparation devoid of contaminating activity, increases ABP activity in the absence of increased intratesticular testosterone. It may be that both hormones are responsible and necessary for continued ABP production. Since a specific receptor for testosterone exists in the Sertoli cell and preliminary experiments suggest that this receptor is translocated into the nucleus as has been described for a variety of steroid hormones, the transcriptional effects previously attributed to FSH may well be due to testosterone. On the other hand, the membrane receptor and cyclic nucleotide mediated events are absolutely dependent upon FSH. Steroid hormones as well as a variety of other peptide hormones will not mimic these responses. Since cycloheximide inhibits the induction of androgen binding protein regardless of the peptide hormone used, it is very possible that FSH may play a role in the translational control of protein synthesis.