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

Neonatal testosterone exposure protects adult male rats from stroke

BACKGROUND

Men have a higher stroke incidence compared to women until advanced age. The contribution of hormones to these sex differences has been extensively debated. In experimental stroke, estradiol is neuroprotective, whereas androgens are detrimental. However, prior studies have only examined the effects of acute treatment paradigms; therefore, the timing and mechanism by which ischemic sexual dimorphism arises are unknown.

METHODS

The effects of exogenous neonatal androgen exposure on subsequent injury induced by middle cerebral artery occlusion in adulthood in male rats were examined. Rats were administered vehicle (oil), testosterone propionate (TP) or the non-aromatizable androgen dihydrotestosterone (DHT) for 5 days after birth. At 3 months of age, a focal stroke was induced.

RESULTS

Testosterone-treated rats (but not DHT-treated animals) had decreased infarct volumes (20 vs. 33%, p < 0.05) as well as increased estradiol levels (39.4 vs. 18.6 pg/ml, p < 0.0001) compared to oil-treated animals. TP-injected males had increased testicular aromatase (P450arom) levels (3.6 vs. 0.2 ng/ml, p < 0.0001) compared to oil-treated males. The level of X-linked inhibitor of apoptosis, the primary endogenous inhibitor of caspase-induced apoptosis, was increased in TP-treated rats compared with the oil-treated males.

CONCLUSIONS

Neonatal exposure to exogenous testosterone upregulates testicular aromatase expression in male rats and leads to adult neuroprotection secondary to changes in serum estradiol levels and cell death proteins. This study suggests that early exposure to gonadal hormones can have dramatic effects on the response to adult cerebrovascular injury.

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

Oestradiol enhances follicle stimulating hormone (FSH) action on seminiferous tubule maturation, but the relative involvement of oestradiol and testosterone remains unclear. This study compares the influences of oestrogen and androgen in FSH and testosterone-deficient rats. Animals were injected daily GnRH-antagonist alone (Ant) or combined with 17β-oestradiol benzoate (EB), or testosterone propionate (TP), or both from post-natal day (pnd) 5 to 15. Hormone levels, tubule growth, cell numbers, germ cell apoptosis and proliferation, and Sertoli cell maturation were evaluated on pnd 16. Ant decreased serum FSH and testosterone levels to ∼60% and ∼50% of control values, respectively, and decreased tubule growth, Sertoli cell number and maturation. Germ cell number declined by apoptosis. Co-administration of EB stimulated spermatogonia proliferation and maintained FSH levels (86% of control). Tubule growth, Sertoli cell number and spermatocyte apoptosis remained normal after TP co-administration, but Sertoli cell maturation, germ cell number and spermatogonia survival were reduced. Co-administration of EB with TP prevented all inhibitions. In conclusion, administration of oestradiol with testosterone, but neither one alone, protected seminiferous tubule maturation against inhibition caused by Ant-induced disruption. Oestrogen was involved in stimulating germ cell proliferation and the maintenance of Sertoli cell maturation, whereas androgen affected seminiferous tubule growth and spermatocyte survival.