Histometric study of the pituitary in mice treated neonatally with steroids and the relationship between prolactin cells and mammary tumorigenesis

“Natural” progesterone: information on fetal effects

BACKGROUND

A variety of progestational agents have been used therapeutically and evaluated for adverse effects over the last 50 years. However, progesterone itself has come into use as a therapeutic agent only recently with the development of an orally bioavailable "micronized" preparation.

METHODS

The current review examines progesterone adverse effects as identified in the larger literature on the toxicity of progestational agents and pharmacokinetics.

RESULTS

Progesterone has cytoplasmic and membrane receptors in a variety of reproductive and nonreproductive tissues including the brain and is a potent inhibitor of GnRH. Limited information is available on progesterone receptors and actions in the fetus. Concern about exogenous progestagen effects on fetal reproductive tract development have led to considerable human research over the years, but this literature review demonstrates that contemporary developmental toxicology research on progesterone is lacking.

CONCLUSIONS

Progesterone is a potent, multi-faceted endocrine agent with an expanding therapeutic profile and a minimal scientific database for evaluating safe use during pregnancy.

Perinatal exposure to estrogenic compounds and the subsequent effects on the prostate of the adult rat: evaluation of inflammation in the ventral and lateral lobes

Although the effects of estrogenic compounds administered during the perinatal period on the size and morphology of the prostate have been well documented, the effects of such exposures on inflammatory changes in the prostate have not been well characterized. Since neonatal estradiol exposure has been shown to cause periods of hyperprolactinemia later in life and a relationship exists between high prolactin levels and rat lateral prostate inflammation, we hypothesized that an exposure to environmental compounds with estrogenic activity could result in an increase in lateral prostate inflammation in adulthood. To investigate this possibility and compare differences between estrogen agonists and antagonists, we examined the effect of a perinatal exposure to 17beta-estradiol, the insecticide methoxychlor, the partial estrogen agonist tamoxifen, and the pure antiestrogen ICI 182,780. Dams were dosed from gestation day (GD)18 to parturition and then the pups were dosed from postnatal day (PND) 1 to 5 with 0.1 mL of a solution of 0.355 mM and .0178 mM by sc injection, respectively, of all compounds in sesame oil, except for methoxychlor, which was administered only to the dam by gavage from GD 18 through PND 5 at a dose of 50 mg/kg in sesame oil. At 90 d of age, the weight of the lateral and ventral prostate in the estradiol group was significantly decreased. Tamoxifen caused a decrease in the weight of the lateral prostate, whereas the ventral lobe was not affected. ICI 182,780 did not alter prostate weight. The methoxychlor exposure increased the lateral lobe weight, but the ventral lobe weight was not affected. In the estradiol and tamoxifen groups, an inflammatory infiltrate was observed in the ventral prostates in 45.0 and 27.8% of the animals, respectively. There was a significant increase in the percent and severity of inflammation in the lateral prostate (as determined by a myeloperoxidase or neutrophil quantification assay) in the estradiol, tamoxifen, and methoxychlor groups as compared to controls. The ICI group was comparable to the controls in both ventral and lateral lobes. This study demonstrates that perinatal exposure to estrogenic compounds can result in alterations in the size of the adult prostate and increase the incidence of prostatitis.

Histologic, morphometric, and immunocytochemical analysis of myometrial development in rats and mice: II. Effects of DES on development

The effects of diethylstilbestrol (DES) treatment on myometrial development from the prenatal to adult period were examined in rats and mice by histologic and immunocytochemical methods using anti-actin, -vimentin, and -laminin to assess cytodifferentiation of smooth muscle and fibroblastic cells, and by morphometric procedures to assess quantitatively the effect of DES on the expression of cellular orientation in the emerging inner circular myometrial layer. Neonatal rats and mice were treated with DES from day 0 (day of birth) to day 2 with dosages known to perturb myometrial development. Neonatal treatment with DES increased the degree of circular orientation within the uterine mesenchyme, an effect detectable following as little as 24 hr of DES treatment. This effect on spatial organization of the mesenchyme was followed by an increase in the thickness of the actin-positive middle layer (prospective circular myometrium) of uterine mesenchyme during days 3-15; from day 15 onward, however, the circular myometrial layer began to fragment into irregular bundles of smooth muscle, and the longitudinal myometrial layer became thinner and more irregularly organized than controls. Vimentin localization in rats treated with DES neonatally was more intense than in controls within the circularly orientated uterine mesenchyme at 5 days. By 60 days the circular and longitudinal myometrial layers of DES-treated animals showed strands and bundles of vimentin-positive cells, which were not present in controls. Both rats and mice show comparable effects of DES treatment.

Effects of neonatal treatment with diethylstilbestrol and 17 alpha-hydroxyprogesterone caproate on in vitro pituitary prolactin secretion

The effects of neonatal hormone treatment with diethylstilbestrol (DES) and 17 alpha-hydroxyprogesterone caproate (HPC) on days 1-5 of life on serum prolactin (PRL) levels and 3H-PRL synthesis and release were studied in C3H/MTV+ mice at 2, 4, 6, 8 and 10 weeks of age. Neonatal treatment of mice with 2.5 micrograms/day DES was the only treatment that affected the developmental pattern of serum PRL levels. Serum PRL levels were significantly decreased at 6 wks of age with this dose of DES. Neonatal treatment with 2.5 micrograms/day DES and 150 micrograms/day HPC affected the developmental pattern of H-PRL synthesis by the pituitary. At 10 wks of age 3H-PRL synthesis was significantly decreased by these doses of DES and HPC. The percent of 3H-PRL released did not differ between neonatally hormone treated and control animals, suggesting that neonatal treatment affected mechanisms that regulate PRL synthesis but not those that regulate release.

The role of 7, 12 DMBA and three hormones in 7, 12 DMBA-induced rat mammary cancer: three hypotheses

The investigation of the role of hormones in the development of hormone-dependent cancers is an interesting and important area of cancer research. A popular mode of examining this area is through experiments with rat or mouse mammary cancer induced by the potent carcinogen, 7, 12 dimethyl (alpha) benzanthracene (7, 12 DMBA). This paper looks at the action of three specific hormones--estrogen, progesterone and prolactin--in the 7, 12 DMBA-induced mammary cancers. Three hypothesis for their action are examined: 1) the hormone as a carcinogen, 2) the hormone as a regulator or neoplasia, and 3) the hormone as both an initiator and a regulator of neoplasia. Although the third hypothesis is probably the least popular among researchers, it will be suggested that it is the most comprehensive and the most complete in that it accounts for evidence giving rise to the first two hypotheses by incorporating both of them. The base of this third hypothesis as presented here is the structural homologies between steric hormones and 7, 12 DMBA. It is suggested that these homologies allow 7, 12 DMBA to interfere with normal hormonal action, and that this interference results in the development of these rat mammary tumors.

Ovarian influence on mitogen responsiveness of lymphocytes from mice neonatally exposed to diethylstilbestrol

Treatment of neonatal female mice with diethylstilbestrol (DES) resulted in a reduced response of spleen lymphocytes to concanavalin A (Con A) and lipopolysaccharide (LPS). Ovariectomy or ovariectomy plus estradiol treatment had no influence on the response to Con A in either control or DES-treated females. Ovariectomy reduced the response to LPS in control animals and eliminated the difference between control and DES-treated females. Estradiol treatment enhanced the response of ovariectomized control females to LPS and restored the difference between control and DES-treated animals. Comparison of the mitogen responsiveness during various stages of the estrous cycle showed a tendency for the response to be augmented at proestrus and metestrus, although the differences were not significant.

Long-term effects of neonatal DES treatment on plasma prolactin in female mice

Prolactin was measured with a homologous radioimmunoassay in plasma samples from adult female NMRI mice injected with 5 micrograms diethylstilbestrol (DES females) or olive oil for the first five days after birth. Estradiol treatment of 6-month-old ovariectomized DES females resulted in markedly higher plasma prolactin concentration compared with the conditions in similarly treated but neonatally olive oil injected females; for both groups the concentrations decreased to the same and very low level after treatment with bromocriptine. The results suggest that DES treatment of neonatal mice enhances the capacity of the pituitary to release prolactin in response to estrogen in later life.