Effects of hemicastration at various ages and of oestradiol-17  on plasma concentrations of gonadotrophins and androgens, testicular growth and interstitial cell responses in prepubertal lambs

Abstract

The effect of the removal of one testis from cross-bred lambs at 1, 4, 8 or 12 weeks of age on plasma FSH, LH and testosterone was studied until 16 weeks of age. Hemicastration at all ages elicited a significant increase in plasma FSH compared to controls without a corresponding change in plasma LH or testosterone. The raised FSH after hemicastration at 1 or 4 weeks of age was suppressed to control levels between weeks 7 and 8; such a suppression was not observed in the 4 weeks following hemicastration at 8 or 12 weeks of age. The weight of the remaining testis had increased compared with the control by 12 weeks of age after hemicastration at 1 week (+ 69%), 4 weeks (+ 13%) and 8 weeks (+ 40%); hemicastration at 12 weeks of age also resulted in growth of the remaining testis at 16 weeks (+ 82%). The total androgen production of interstitial cells in response to ovine LH stimulation in vitro did not differ significantly between lambs of 1 and 12 weeks of age, or in animals of 4, 8 and 12 weeks of age after hemicastration at 1 week of age. Subdermal implantation of oestradiol-17 beta into 1-week hemicastrated lambs at the time of operation or at 6 weeks of age increased plasma oestradiol concentrations by approximately 2-4-fold, prevented the FSH and testicular growth responses to hemicastration and suppressed plasma LH and testosterone to levels lower than those in control lambs. The total androgen response of interstitial cells from the remaining testis of oestradiol-implanted lambs at 12 weeks of age was significantly reduced. We suggest that the pituitary-testis axis varies in sensitivity during the prepubertal period although the interstitial cellular response of the testis to LH stimulation remains constant.

Development of the seminiferous tubules after neonatal hemicastration in the boar

“…However, since seminiferous tubule diameter did not change, and proliferation of Sertoli cell numbers has been reported previously after hemicastration in boars and several other species (Jenkins & Waites, 1983;Waites et al, 1983;Orth et al, 1984;Hochereau de Reviers et ai, 1984;Putra & Blackshaw, 1985), the compensatory increase in mass of Sertoli cells observed here is probably due to proli¬ feration of Sertoli cell numbers.…”

“…(Colenbrander et ai, 1978;Herrera et al, 1983;Kosco et al, 1987). Compensatory testicular growth and proliferation of Sertoli cells in neonatally hemicastrated bulls and rams, respectively, is delayed until there is a significant elevation in plasma testosterone concentration (Boockfor et (Barnes et al, 1980b;Boockfor et al, 1983;Jenkins & Waites et al, 1983;Waites et al, 1983;Kosco et al, 1987) indicates that intratesticular testosterone production is greater in Group-HC than in Group-I boars (Lindner & Rowson, 1961;Moger et al, 1985). Compensatory increase in testicular weight, seminiferous tubule length and Sertoli cell numbers was drastically reduced in boars hemicastrated at 3-5 months of age in comparison to those hemicastrated at 1 or 2 months (Putra & Blackshaw, 1985).…”

The functional maturation of the Sertoli cell and Leydig cell in the mammalian testis

“…The altered androgen production may be stimulated indirectly by the FSH acting on Sertoli cells since an increase in LH secretion in response to hemicastration is less evident. The sensitivity of Leydig cells to LH is increased after hemicastration in bulls (Boockfor, Barnes & Dickey, 1983) but not in lambs (Jenkins & Waites, 1983 …”

“…Despite this, the total production of oestrogen remains at < 0-1 % of androgen output in most mammalian species, with the exception of the stallion and boar (Amann & Schanbacher, 1983). Implants of oestradiol depress plasma androgen concentrations in lambs (Jenkins & Waites, 1983), and conversely immunization against oestradiol stimulates androgen production in rats (Nishihara & Takahashi, 1983) (Brinkmann, Mulder, Lamerstahlhofen, Mechielsen & van der Molen, 1972;Moger, 1980;Benahmed, Bernier, Ducharme & Saez, 1982), the concen¬ trations of oestradiol required to impair the steroidogenic function of Leydig cells directly are probably never achieved in vivo, and therefore a suppression of LH secretion is a more likely explanation of the effects of oestradiol on androgen production. (Sharpe, 1982(Sharpe, , 1984.…”

Testicular Weight, Sertoli Cell Number, Daily Sperm Production, and Sperm Output of Sexually Mature Rabbits after Neonatal or Prepubertal Hemicastration1

“…In many species, the removal of one testis elicits a compensatory hypertrophy of the remaining testis, which has been characterized chiefly as an increase in testicular weight [1][2][3][4][5][6][7][8]. This response appears to be age-dependent, rarely occurring when hemicastration is performed on adult animals [4,[9][10][11][12][13].…”