Administration of testosterone inhibits initiation of seminal tubule growth and decreases Sertoli cell number in the earliest period of rat's postnatal development.

Abstract

Sertoli cell (SC) number determines testes size and their capacity to produce spermatozoa. In the rat SC proliferate until 15 th postnatal day (PND). Their proliferation is stimulated by FSH and inhibited by estradiol, but the role for androgens is uncertain. In this study we analyzed the effects of testosterone administration on testes growth and SC number in relation to timing of the treatment. Male rats were injected with 2.5 mg of testosterone propionate (TP) from birth until 5 th PND and autopsied either on 6 th PND [TP1-5 (6) Control groups (C) received vehicle. In the Cs serum level of estradiol was 20-fold higher (p<0.001) and FSH was 1,7-fold higher (p<0.05) on 6 th PND than on 16 th PND, while testosterone did not change. After TP blood level of testosterone increased 2200-fold on 6 th PND (p<0.05), and 8-fold on 16 th PND. In turn, continuous TP administrations resulted on 16 th PND in the increase in testosterone serum level by 2000-times of C without influence on FSH. While the treatment from birth either during initial 5 days or continuously until 15 th day decreased testicular weight (p<0.001), tubule length (p<0.05) and SC number (p<0.001), the treatment initiated on 5 th PND had no effects. TP reduced serum estradiol level on 6 th PND by 13-fold (p<0.01), but doubled it on 16 th PND. Conclusion: Neonatal rats secrete estradiol and FSH in the amounts greatly extending those presented during further development. Testosterone inhibits testicular growth and SC number acting during first 5 neonatal days by decreasing FSH secretion, but is not effective during further development. Direct inhibitory influence of testosterone or trough its increased aromatisation to estradiol beyond neonatal period may be responsible for sustained inhibition of testes growth and SC number during infancy.

Neonatal Testosterone Exposure Protects Adult Male Rats from Stroke

“…As seen previously [28], exposure to androgens in early development had profound effects on the testes. Rats exposed to either neonatal TP or DHT had significantly smaller testes compared to vehicle-treated group, suggesting similar peripheral effects of both of these androgens on peripheral tissue (Fig.…”

“…In this cohort, there was no significant difference in testosterone levels between TP and oil groups, but a robust decrease in estradiol was seen in TP group compared with oil controls at PND16. Physiologically, there is an increase in estradiol production in the immediate neonatal period which decreases over several days [28]. One previous study directly examined sertoli cell number and hormone levels in male rats after injection with TP on PND1-5 [28] and found an increase in serum estradiol on PND 16 in TP-treated neonates, but lower levels on PND 6 compared to controls.…”

“…Physiologically, there is an increase in estradiol production in the immediate neonatal period which decreases over several days [28]. One previous study directly examined sertoli cell number and hormone levels in male rats after injection with TP on PND1-5 [28] and found an increase in serum estradiol on PND 16 in TP-treated neonates, but lower levels on PND 6 compared to controls. Our findings suggest that in the immediate weeks after TP injection, testosterone suppresses peripheral aromatase production, preventing estradiol conversion; however as the rat ages, aromatase production in the testes is enhanced and surpasses that of control leading to an enhanced production of estradiol in adulthood.…”

Testosterone and oestradiol in concert protect seminiferous tubule maturation against inhibition by GnRH-antagonist

“…, 2008) without affecting the secretion of LH and FSH (Kula et al. , 2001), and the dose of TP also did not influence FSH secretion in immature rats (Walczak‐Jedrzejowska et al. , 2009).…”

“…The volume density ( V v) of the seminiferous tubules, expressed as a percentage, was obtained by the point counting method described previously (Kula et al. , 2001; Walczak‐Jedrzejowska et al. , 2009).…”