Effects of LH-RH infusion, castration and cryptorchidism on gonadotrophin and testosterone secretion in developing rams

Abstract

Summary. The relationship between the pituitary gland and testis in rams was studied from birth to sexual maturity. The concentrations of LH, FSH and testosterone increased between 5 and 7 weeks of age; the rise was not correlated with any specific cytological change in the testis. An augmented pituitary response to LH-RH was demonstrated as levels of gonadotrophin increased. It is unclear whether this change in sensitivity plays a role in initiation of the pubertal process because Sertoli cell maturation, the earliest detectable change in the seminiferous epithelium, occurs between 17 and 21 weeks of age. Spermatocytes were first seen in biopsies taken at 31–36 weeks and spermatogenesis was established fully by 45 weeks. This second phase of testicular development was characterized by increases in prolactin, testosterone and LH. Leydig cells previously difficult to identify became recognizable at the time of sexual maturation.