Regulação da proliferação pós-natal das células de Sertoli em ratos

Abstract

When indicating the number of spermatozoa produced in an adult animal, the neonatal period, in whichthe final number of Sertoli cells is established in rats, is key. It is believed that the main mitogenic factorof Sertoli cells is the FSH, while the thyroid hormone triiodothyronine (T3) would be responsible for theregulation of the maturation/differentiation of such cells. However, the treatment with the goitrogenicdrug PTU has demonstrated that, despite the plasmatic levels of FSH remain very low during thetreatment period, the transitory hypothyroidism in the neonatal period takes to a sharp increase of theSertoli cells population per testis and sperm production in rodents such as rats, mice, and hamsters.Investigating the degree of proliferation of the Sertoli cells in hypothyroid animals, is the main objective of the present work, in which the FSH secretion was suppressed by the treatment with a powerful GnRHagonist/antagonist (Leuprolide) or GnRH antagonist (Antide). Also, the effect of the neonatal treatmentwith a single dose of leuprolide in the testicular development and the plasmatic levels of FSH of Wistarrats was investigated. The results found during the postnatal development of the testis suggest that thetreatment with leuprolide of long duration promoted initial increase in the proliferation of the Sertolicells, probably due to initial rise of the FSH levels. However, from the first day of treatment, this drugsuppressed the levels of FSH for almost 5 weeks, what probably was responsible for the substantialreduction of the testis weight and the number of Sertoli cells per testis in the adult rats. Although bothleuprolide and antide work as GnRH antagonist, some morphofunctional results found in adult-rat testishad shown that these drugs don t necessarily promote the same effects, specially in relation to thefunction of the Leydig and Sertoli cells that seem to be more compromised in the animals treated withantide. Surprisingly, the treatment with PTU+leuprolide did not provide the expected results for testisweight, for Sertoli cell number per testis and daily sperm production, what remained within the samerange as of those animals treated with PTU. In fact, the results found in rats treated with PTU+leuprolideand sacrificed between 30 and 43 days of age had shown that in this condition the Sertoli cells remainedimmature and with prolonged proliferative capacity, being therefore capable to proliferate during a longertime period in which the FSH levels were probably high after ceasing the suppressor effect of leuprolidein the gonadotropin-releasing hormone (GnRH)