Interaction between prolactin and androgens in the accessory sex organs of male mice

Seasonal Endocrine Changes and Breeding Activity in Mediterranean Wild Ruminants

The methods of assisted reproduction commonly used in domestic animals are currently being applied to non-domestic species. This is because of the limitation of maintaining the genetic variability in the wild, as it occurs in wild ruminants of the Mediterranean Basin. Despite the apparent progress of the technology, success of the offspring to grow and become healthy adult individuals has remained low in wild species. Difficulties usually arise from insufficient information about basic reproductive biology, such as the seasonal changes in ovarian and testicular activity. Directional adaptive evolution involves development of speciespecific physiological reproductive patterns to cope with various environmental factors. Thus, species originating and living at the same latitude display different reproductive strategies to entrain the breeding activity at an optimal time of the year. The aim of this paper was to present current knowledge on reproductive physiology of Mediterranean wild ruminants as a basic prerequisite for the successful use of assisted reproduction methods. Special emphasis is given to seasonal endocrine changes, ovarian cycles and testicular activity of Iberian wild ruminants, together with the role of social interactions on the regulation of these events.

Differences in reproductive pattern between wild and domestic rams are not associated with inter-specific annual variations in plasma prolactin and melatonin concentrations

This study compares morphological changes, performed with real-time transrectal ultrasonography, of testis and accessory glands and seasonal endocrine changes in a wild (Mouflon) and a domesticated (Spanish Merino) breed of sheep. In Mouflons, the maximum plasma testosterone concentrations, testicular diameter and vesicular gland size occurred synchronously during autumn (P<0.001). In Merino rams the highest circulating levels of testosterone (P<0.05) and maximum testicular diameter (P<0.001) occurred during summer, with no seasonal variations in vesicular and bulbourethral glands. The seasonal changes in plasma concentrations of prolactin were not correlated with annual variations in testicular and glandular size in neither wild nor domestic species. No differences were observed between both species for the seasonal pattern of prolactin secretion and mean amplitude of melatonin. Wide differences in reproductive patterns between wild and domestic types of rams do not appear to be attributed to seasonal changes in prolactin and melatonin secretion.

Genetic ablation of the steroid receptor coactivator-ubiquitin ligase, E6-AP, results in tissue-selective steroid hormone resistance and defects in reproduction

The E6-associated protein (E6-AP), although originally identified as a ubiquitin ligase, has recently been shown to function as a coactivator of steroid receptor-dependent gene expression in in vitro assays. In order to determine whether E6-AP acts as a coactivator in vivo, physiological parameters associated with male and female sex steroid action were assessed in the E6-AP null mouse. Gonadal size was reduced in E6-AP null male and female mice in comparison to wild-type controls in conjunction with reduced fertility in both genders. Consistent with this observation, defects in sperm production and function, as well as ovulation were observed. In comparison to wild-type controls, induction of prostate gland growth induced by testosterone and uterine growth by estradiol were significantly reduced. In contrast, estrogen and progesterone-stimulated growth of virgin mammary gland was not compromised by E6-AP ablation despite E6-AP expression in this tissue. This latter finding contrasts with the impaired estrogen and progesterone-induced mammary gland development observed previously for steroid receptor coactivator type 1 (SRC-1) and SRC-3 female knockout mice. Taken together, these results are consistent with a role for E6-AP in mediating a subset of steroid hormone actions in vivo. Nevertheless, differences observed between SRC and E6-AP knockout phenotypes indicate that these two families of steroid receptor coactivators are not functionally equivalent and supports the hypothesis that coactivators contribute to tissue-specific steroid hormone action.

Increase in epithelial cell growth by hyperprolactinemia induces delay of castration-induced involution of mouse seminal vesicle

Male (C57BL/6 x DBA)F1 hybrid mice were castrated on day 60 after birth; two pituitaries from 60-day-old female mice were immediately grafted under the capsule of the left kidney in half of the castrated mice to induce hyperprolactinemia. The seminal vesicles in the absence of androgen treatment were examined 15, 22, 30 and 60 days after castration with or without grafting. Significant increases in the weight (1.3-1.4-fold), DNA content (1.2-1.3-fold) and labeling index of epithelial cells (4-10-fold) of the seminal vesicles were found in mice with pituitary grafts compared to mice without grafts on days 15-30 after castration but not on day 60 after castration. Such stimulatory effects of hyperprolactinemia on mouse seminal vesicle cells were also observed on day 15 after castration plus adrenalectomy. Cell loss from the seminal vesicles was found to be similar in castrated mice with and without the grafts. The present findings demonstrate that hyperprolactinemia induces an increase in DNA synthesis of epithelial cells in the seminal vesicles until 30 days after castration and results in a significant delay of castration-induced involution of the weight and DNA content of the seminal vesicles for 1 month. However, the delay with increased epithelial cell growth by hyperprolactinemia disappeared 60 days after castration.

Androgen-regulated expression of secretory protein synthesis in mouse ventral prostate

Two proteins of molecular weights 25 and 12 kDa (p25 and p12 respectively), whose expression is regulated by testosterone, were identified in mouse ventral prostate. An antiserum raised to mouse ventral prostate secretion was used to demonstrate that p25 corresponds to the major secretory glycoprotein in mouse prostatic fluid. This antiserum does not cross-react with the major secretory proteins of the rat ventral prostate. Western blot analysis of mouse ventral prostate proteins using the prostatic secretion antiserum demonstrates that p12 and p25 are detectable at 3 weeks of age, but the maximum level of both proteins is not attained until 5 weeks of age. In addition, synthesis of p25 was also observed in prostate tissue derived from differentiated embryonic urogenital sinus tissue growing as implants under the renal capsule of syngeneic male hosts.

Mechanisms in the production of prepuberal reproductive defects in neonatal estrogenized male rats

Neonatal estrogenization induced in prepubertal males atrophy of the testis and ventral prostate and increased the weight of the seminal vesicles. Atrophy of the testis was probably due to the inhibition of FSH and LH secretion: males estrogenized on day one and sacrificed daily from day six to day fifteen showed lower gonadotropin levels than their respective controls. In addition, daily FSH and LH administration (80 micrograms/100 g BW and 40 micrograms/100 g BW respectively) from day one to day fifteen increased testicular development more effectively in estrogenized than in control males and the differences between the two groups disappeared. Prostate atrophy was due to the decreased testosterone secretion. The reason for the hypertrophy of the seminal vesicles remains unclear: reduction in Prolactin levels due to bromocriptine treatment did not normalize the seminal vesicles weight, indicating that hyperprolactinemia was not the cause. Male rats estrogenized on day one, orchidectomized on day 5 and decapitated on day fifteen also showed hypertrophy in their seminal vesicles. These results indicate that testicular factors, other than testosterone, were not responsible for the vesicular hypertrophy. It seem possible that estrogens might act directly on vesicular growth.

Impact of prolactin on the growth rate pattern and biochemical components of accessory sex organs of male albino rats during puberal transition

Prolactin (PRL) was administered subcutaneously to different age-groups of male albino rats across the puberal transition. The tissue somatic indices (TSI) and organic components of accessory sex organs were increased in the presence of PRL at all the age-groups. The participation of PRL in the acceleration of maturation events of accessory sex organs was age-dependent.