Effect of prolactin on the water-salt balance in rat females in the model of cholestasis of pregnancy.

We studied the possibility of prolactin involvement in the regulation of water-salt metabolism in female rats in the model of cholestasis of pregnancy. For simulation of the prolactin level during pregnancy, hyperprolactinemia was simulated by transplantation the pituitary under the renal capsule of the recipient; for modeling cholestasis of pregnancy, a combination of induced hyperprolactinemia and bile duct obstruction was used. Diurnal diuresis, expression of aquaporin 1-4 mRNA in the renal medulla, glomerular filtration rate, and diurnal sodium excretion were evaluated in these models. Diuretic and natriuretic effects of prolactin in the model of cholestasis of pregnancy were demonstrated. These data and the fact that prolactin has no effect on glomerular filtration rate and aquaporin expression suggest that prolactin modulates activity of sodium transporters in the kidney.

Functional Restoration of Pituitary after Pituitary Allotransplantation into Hypophysectomized Rats.

Long-term hormone replacement therapy due to panhypopituitarism can lead to serious complications and thus, pituitary transplantation is considered a more desirable. We investigated functional restoration after allotransplatation of the pituitary gland. We transplanted extracted pituitary gland into the omentum of an hypophysectomized rat. Two experiments were performed: (1) to confirm the hypophysectomy was successful and (2) to assess functional restoration after pituitary transplantation. Pituitary hormone level and weight change were consecutively assessed. Electron microscopic (EM) examinations were performed to identify morphological changes at 3 days after transplantation. We confirmed that pituitary gland was properly extracted from 6 rats after sacrifice. The findings showed (1) a weight loss of more than 3% or (2) a weight change of less than 2% along with a decreased growth hormone (GH) level by more than 80% at 2 weeks post-hypophysectomy. A further four rats underwent pituitary transplantation after hypophysectomy and were compared with the previously hypophysectomized rats. All showed rapid weight gain during the two weeks after transplantation. The thyroid-stimulating hormone, prolactin, and GH levels were restored at one week post-transplantation and maintained for 10 weeks. Hypophyseal tissue architecture was maintained at 3 days after transplantation, as indicated by EM. These data suggest that a transplanted pituitary gland can survive in the omentum with concomitant partial restoration of anterior pituitary hormones.

From Pituitary Stem Cell Differentiation to Regenerative Medicine.

The anterior pituitary gland is comprised of specialized cell-types that produce and secrete polypeptide hormones in response to hypothalamic input and feedback from target organs. These specialized cells arise during embryonic development, from stem cells that express SOX2 and the pituitary transcription factor PROP1, which is necessary to establish the stem cell pool and promote an epithelial to mesenchymal-like transition, releasing progenitors from the niche. Human and mouse embryonic stem cells can differentiate into all major hormone-producing cell types of the anterior lobe in a highly plastic and dynamic manner. More recently human induced pluripotent stem cells (iPSCs) emerged as a viable alternative due to their plasticity and high proliferative capacity. This mini-review gives an overview of the major advances that have been achieved to develop protocols to generate pituitary hormone-producing cell types from stem cells and how these mechanisms are regulated. We also discuss their application in pituitary diseases, such as pituitary hormone deficiencies.

Effect of thyroxin on cell morphology and hormone secretion of pituitary grafts in rats.

INTRODUCTION: Growth hormone and prolactin secretion is affected by thyroid hormones. To see if this influence is subsidiary to the hyptothalamus, we investigated the effects of thyroxin (T4) on hormone secretion and histology of sellar pituitaries and pituitary grafts detached from the hypothalamus (autografted or allografted under the kidney capsule). MATERIALS AND METHODS: Male Wistar rats were divided into eight groups: control, thyroidectomised, pituitary autografted, pituitary allografted, and four additional groups that were injected with T4 for two weeks, starting four weeks after surgery. At sacrifice, adenohypophysial hormone blood levels were assessed, and tissue from sellar and grafted pituitaries were investigated by histology and electron microscopy. RESULTS: Growth hormone and prolactin blood levels, as well as the number of growth hormone immunopositive cells increased in T4-treated groups. Both pituitary auto- and allo-grafts showed lactotroph hyperplasia and displayed spongiform areas containing cells with vesicles in their cytoplasm resembling thyroidectomy cells. This phenomenon was minimized in their respective T4-treated group. Thyroidectomy cells were identified in pituitary grafts, indicating that hypothalamic control was not essential to induce them. DISCUSSION AND CONCLUSION: It is intriguing that the pituitary allografted group, even maintaining normal T4 blood levels, developed thyroidectomy cells in their grafts, suggesting that a long- term deficit of vascularization (>4 weeks) prevented T4 from reaching the graft. After 6 weeks, post T4 treatment of two weeks seemed to be the determining factor to minimize thyroidectomy cells in both pituitary autografted + T4 and pituitary allografted + T4 grafts compared to the untreated groups, although more time and/or higher T4 doses may be required to fully restore the euthyroid morphology.

Hair color, molt, and testis size in male, short-tailed weasels treated with melatonin.

Melatonin in beeswax was implanted in male weasels (Mustela erminea). Brown weasels and white animals undergoing the spring change to the brown pelage and reproductive activity molted, grew a new white coat, and became reproductively quiescent after treatment. Controls retained or acquired the brown coat and developed or maintained enlarged testes. Treated weasels with pituitary autografts under the kidney capsule grew brown hair after hair growth was initiated by plucking. It is suggested that the pineal gland product, melatonin, initiates changes in the central nervous system and endocrines which result in molting, growth of the white winter pelage, and reproductive quiescence in the weasel.

Long-term, homologous prolactin, administered through ectopic pituitary grafts, induces hypothalamic dopamine neuron differentiation in adult Snell dwarf mice.

Pituitary prolactin (PRL) secretion is inhibited by dopamine (DA) released into the portal circulation from hypothalamic tuberoinfundibular DA (TIDA) neurons. Ames (df/df) and Snell (dw/dw) dwarf mice lack PRL, GH, and TSH, abrogating feedback and resulting in a reduced hypophysiotropic TIDA population. In Ames df/df, ovine PRL administration for 30 d during early postnatal development increases the TIDA neuron number to normal, but 30 d PRL treatment of adult df/df does not. The present study investigated the effects of homologous PRL, administered via renal capsule pituitary graft surgery for 4 or 6 months, on hypothalamic DA neurons in adult Snell dw/dw mice using catecholamine histofluorescence, tyrosine hydroxylase immunocytochemistry, and bromodeoxyuridine immunocytochemistry. PRL treatment did not affect TIDA neuron number in normal mice, but 4- and 6-month PRL-treated dw/dw had significantly increased (P < or = 0.01) TIDA (area A12) neurons compared with untreated dw/dw. Snell dwarfs treated with PRL for 6 months had more (P < or = 0.01) TIDA neurons than 4-month PRL-treated dw/dw, but lower (P < or = 0.01) numbers than normal mice. Periventricular nucleus (area A14) neuron number was lower in dwarfs than in normal mice, regardless of treatment. Zona incerta (area A13) neuron number was unchanged among phenotypes and treatments. Prolactin was unable to induce differentiation of a normal-sized A14 neuron population in dw/dw. Bromodeoxyuridine incorporation was lower (P < or = 0.01) in 6-month PRL-treated normal mice than in 6-month PRL-treated dwarfs in the subventricular zone of the lateral ventricle and in the dentate gyrus, and lower (P < or = 0.05) in 4-month untreated dwarfs than in 4-month untreated normal mice in the median eminence and the periventricular area surrounding the third ventricle. Thus, a PRL-sensitive TIDA neuron population exists in adult Snell dwarf mice when replacement uses homologous hormone and/or a longer duration. This finding indicates that there is potential for neuronal differentiation beyond early developmental periods and suggests plasticity within the mature hypothalamus.

[Transplantation of hormone-producing cells into the testicular paravasal fat hole in secretory infertility and gonadal hypoplasia].

Intratesticular cell transplantation is an effective surgical method in the treatment of patients with secretory infertility in chronic orchoepididymitis accompanied and not accompanied with marked testicular hypoplasia. This treatment in patients with secretory infertility and testicular hypoplasia enlarges gonads by more than 60% (from 3 to 5 mm3). The density of spermatozoa on the spermogram of males both with and without testicular hypoplasia increased by more than 70%--from 7.2 to 12.2 mln/ml in patients with gonad hypoplasia and from 14.2 to 25.5 mln/ml in patients with normal testicular size. The number of active mobile spermatozoa rose by 76 and 32% in patients with and without testicular hypoplasia, respectively, the number of pathological cells in ejaculate decreased from 61.8 to 51.4% and from 48.2 to 41.2%, respectively. Cell transplantation enabled a wife of each seventh man with secretory infertility to have a child, even in case of severe bilateral testicular hypoplasia in two of the men.

Mice lacking the amplified in breast cancer 1/steroid receptor coactivator-3 are resistant to chemical carcinogen-induced mammary tumorigenesis.

Amplified in breast cancer 1 (AIB1; steroid receptor coactivator-3, p/CIP, RAC3, ACTR, TRAM-1, or NCoA-3) is a transcriptional coactivator for nuclear receptors and certain other transcription factors and is a newly defined oncogene overexpressed in human breast cancer. Although the role and molecular mechanism of AIB1 in normal physiology and in breast cancer are currently under intensive investigation, the role of AIB1 in determination of the susceptibility of mammary gland to chemical carcinogens remains uncharacterized. In this study, we used back-crossed FVB wild-type (WT) and AIB1 mutant mice to assess the role of AIB1 in mammary gland development and in carcinogen-induced tumorigenesis. We show that mammary ductal growth was delayed in AIB1-/- mice with FVB strain background, and mammary ductal outgrowths emanating from the AIB1-/- mammary epithelial transplants in WT mice also were attenuated, indicating that the role of AIB1 in mammary ductal growth is a mammary epithelial autonomous function. In mice treated with the chemical carcinogen 7,12-dimethylbenz[a]anthracene (DMBA), AIB1 deficiency protected the mammary gland, but not the skin, from tumorigenesis. AIB1 deficiency suppressed the up-regulation of the insulin receptor substrate (IRS)-1 and IRS-2 and thereby inhibited the activation of Akt, expression of cyclin D1, and cell proliferation. The suppression of these components for insulin-like growth factor-I signaling might be partially responsible for the decreased DMBA-induced mammary tumor initiation and progression in AIB1-/- mice. Our results suggest that AIB1 may serve as a potential target for prevention of carcinogen-induced breast cancer initiation and for treatment of breast cancer progression.

Deiodinase type 1 activity is expressed in the prostate of pubescent rats and is modulated by thyroid hormones, prolactin and sex hormones.

The aim of this study was to characterize the type of 5'-deiodinase activity in the prostate of pubescent rats (7-8 weeks), to establish its distribution in the lobes (ventral, dorsolateral, and anterior), and to analyze its modulation by prolactin (PRL), testosterone, dihydrotestosterone (DHT), and 17beta-estradiol (E(2)). Our results showed that the enzymatic activity was highly susceptible to inhibition by 6-n-propyl-2-thiouracil and gold thioglucose, its preferential substrate was reverse tri-iodothyronine (rT(3)), it exhibited a low dithiothreitol requirement (5 mM), and the apparent K(m) and V(max) values for substrate (rT(3)) were approximately 0.25 microM and 9.0 pmol liberated/mg protein per hour, respectively. All these characteristics indicate the preferential expression of type 1 deiodinase (D1), which was corroborated by demonstrating the presence of D1 mRNA in prostate. D1 activity was detected in all lobes and was most abundant in the dorsolateral. Although we detected type 2 deiodinase (D2) mRNA expression, the D2 activity was almost undetectable. D1 activity was enhanced in animals with hyperthyroidism and hyperprolactinemia, in intact animals treated with finasteride (inhibitor of local DHT production), and in castrated animals with E(2) replacement. In contrast, activity diminished in castrated animals with testosterone replacement. Our results suggest that thyroid hormones, PRL, and E(2) exert a positive modulation on D1 activity, while testosterone and DHT exhibit an inhibitory effect. D1 activity may be associated with prostate maturation and/or function.

Experimental adenomyosis.

Adenomyosis has been reported in a number of different animal species, whereas endometriosis appears limited to humans and non-human primates. This suggests a different aetiology of the two conditions. Adenomyosis develops spontaneously in certain strains of laboratory mice. Its incidence in mice can be markedly enhanced by systemic exposure to various hormonal agents, including prolactin, progesterone, synthetic progestins, certain oestrogenic agents, as well as tamoxifen and toremifene. The precise hormonal changes necessary remain unclear, although the evidence suggests that adenomyosis in this model is not due to a simple oestrogenic effect. Study of the pathological and molecular alterations in this model indicates that disturbances to the uterine stroma, blood vessels and myometrium are also important factors in the development of adenomyosis.

Effects of partial decerebration and hypophyseal allograft in the thymus of chicken embryos: thymostimulin localization and enzymatic activities.

Changes in chicken embryo thymus after partial decerebration (including the hypophysis) and hypophyseal allograft were investigated. Chicken embryos were partially decerebrated at 36-40 hr of incubation and on day 12 received a hypophyseal allograft from 18-day-old donor embryos. The embryonic thymuses were collected on day 18 and examined with histological methods, tested for the anti-thymostimulin-like immune-reaction, and for histoenzymatic activities and compared with normal and sham-operated embryos at the same age. After partial decerebration, the thymic cortical and medullary compartments diminished markedly in size. Anti-thymostimulin, succinic dehydrogenase and ATPase enzymatic activities tested, yielded negative reactions. In partially decerebrated hypophyseal allografted embryos, the same thymic compartments improved and anti-thymostimulin-like immune-reaction and enzymatic activities partially recovered. These findings confirmed the key role of hypophysis in thymic ontogenic development and provided new information in metabolic enzymatic pathways and synthesis of a thymostimulin-like substance in the thymus.

Development of pancreatic hyperplasia in female SHN mice receiving ectopic pituitary isografts.

The long-term effects on pancreas of ectopic pituitary grafting at various sites were studied in female SHN mice. Hyperprolactinemia induced by pituitary grafting resulted in an increase in the pancreatic weights, mainly due to hyperplastic proliferation of the pancreatic acinar glands. In addition, islet-cell hyperplasia and adenoma were found in the pituitary-grafted mice. Hyperplastic nodules resembling adenoma of the pancreatic acinar cells were also induced by pituitary grafting. The pancreata of mice with pituitary grafts frequently adhered to the uterus, ovary, and other organs; some of the pancreata further invaded these organs. Control mice bearing no pituitary grafts showed no pancreatic lesions. These results indicate the participation of prolactin in pancreatic tumorigenesis.

Mammary tumorigenesis in chemical carcinogen-treated mice. VI. Tumor-producing capabilities of mammary dysplasias in BALB/cCrgl mice.

Two types of mammary dysplasias occurring in 7,12-dimethylbenz[a]anthracene (DMBA)-treated BALB/cCrgl mice were transplanted into the cleared mammary fat pads of syngeneic mice for an assessment of their growth behavior and tumor potentials. Keratinized nodules, numerous in DMBA-treated, pituitary isograft-bearing BALB/cCrgl mice, produced primarily ductal outgrowth in control mice and very few tumors (7%) 56 weeks after transplantation. Such dysplasias transplanted into mice bearing pituitary isografts exhibited lobuloalveolar development and produced a higher incidence of tumors (32%). Hyperplastic alveolar nodules (HAN), though relatively rare in DMBA-treated BALB/cCrgl mice, produced lobuloalveolar outgrowth in control mice and had a 100% tumor incidence. Four HAN outgrowth lines were developed by serial transplantation of samples of the nodule outgrowths. The tumor potentials of these nodule lines in intact controls and ovariectomized mice was determined over several transplant generations. The tumor potentials of two of the three nodule lines were decreased in the absence of ovarian hormones. However, the growth of 23 mammary tumors derived from these nodule lines and of nine derived from in situ primary tumors was unaffected by the absence of the ovary. These results, along with those published previously, suggest that mammary tumors in chemical carcinogen-treated mice arise from several precursor populations. These preneoplastic populations comprise both alveolar and ductal hyperplasias.

Effects of exposure of neonatal mice to 17beta-estradiol on subsequent age-incidence and morphology of carcinogen-induced mammary dysplasia.

Mice exposed to estrogens as neonates developed more mammary dysplasias and had different morphologic types of dysplasias than did normal animals when both groups were exposed to a carcinogen: 1) before puberty, 2) during active mammary growth, 3) or at 6 months of age (the time when spontaneous dysplasias begin to appear in normal animals). The relative percentages of various morphologic types of dysplasias differed in hosts that received different treatments. The significance for subsequent patterns of mammary disease caused by exposure of neonates to 17beta-estradiol was discussed.

N-nitroso-N-methylurea-induced mammary tumors in the rat: role of prolactin and a prolactin-lowering drug.

Female outbred Sprague-Dawley rats bearing N-nitroso-N-methylurea (NMU)-induced mammary tumors received various endocrine therapies 3 months after the first NMU injection. Rats were divided into 5 groups (15-20 rats/group) and received a 4-week treatment as follows: group 1, controls; group 2, ovariectomized; group 3, 0.5 mg 2-bromoergocryptine (CB-154) injected so twice daily; group 4a, pituitary implant under the kidney capsule; and group 4b, CB-154 injected during the last 2 weeks of the experiment in rats bearing a pituitary implant. Castration of rats with established NMU-induced tumors resulted in a decrease in both tumor number and size, but these parameters again started to increase 3 weeks post castration. CB-154 failed to reduce the tumor number but did arrest the increase in tumor size. In the animals with a pituitary implant, both tumor number and tumor size increased progressively at a greater rate than in control animals, whereas the addition of CB-154 (group 4b) stabilized the tumor growth. Ovariectomy (OVX) resulted in a significant decline of steroid receptor levels. Prolactin (PRL) receptor levels were significantly stimulated by the pituitary implant, and CB-154 prevented this increase. The present studies confirmed that NMU-induced mammary tumors are less hormone-dependent (response to OVX) than 7,12-dimethylbenz[a]anthracene (DMBA)-induced tumors. The role of PRL also appears to be less important, at least for established tumors, for NMU-induced mammary tumors than for DMBA-induced mammary tumors.

Influence of prolactin on carcinogen-induced leukemogenesis in Long-Evans rats.

Hypophysectomy of rats bearing 7,12-dimethylbenzanthracene-induced leukemia has been reported to result in a prompt and persistent regression of the leukemia. The purpose of this study was to determine whether or not marked alterations in prolactin secretion would influence this neoplastic process. To determine this, immature male and female Long-Evans rats were divided into three groups: Group 1, controls; Group 2, pituitary grafted (hyperprolactinemia); and Group 3, 2-bromo-alpha-ergocryptine-treated (hypoprolactinemia). Two weeks after the initial treatment and at 2-week intervals thereafter (6 total), each rat was given a single intragastric intubation of 7,12-dimethylbenzanthracene (10 mg/rat). Two months after the initial carcinogen treatment and at 2- to 3-week intervals thereafter, all rats had liver biopsies for the identification of leukemia. Results clearly show that despite nearly 10-fold difference in mean serum prolactin levels in the three groups of female rats and nearly a 20-fold difference in the level of this hormone in male rats, no significant differences in the magnitude of this leukemogenic process could be detected. Thus, striking changes in prolactin secretion do not appear to influence significantly this leukemogenic process.

Recovery of transformed nodule and ductal mammary cells from carcinogen-treated C57BL mice.

Transformed nodule and ductal mammary cells were recovered by cell dissociation and transplantation of mammary cells from C57BL/Crgl mice treated with 7,12-dimethylbenz(a)anthracene. Four-week-old mice were divided into the following groups: Group A, not treated; Group B, 2 pituitary isografts under the kidney capsule; Group C, 1.0 mg 7,12-dimethylbenz(a)anthracene intragastrically at 5 and 6 weeks of age; and Group D, 2 pituitary isografts and 1.0 mg 7,12-dimethylbenz(a)anthracene intragastrically at 5 and 6 weeks of age. At 10, 14, 18, and 22 weeks of age, the mammary glands were enzymatically dissociated, and 10(5) cells were injected into the gland-free mammary fat pads of 3-week-old syngeneic mice. After 10 weeks, the outgrowths were examined and classified as ductal, ductal dysplasia, or hyperplastic alveolar nodule. Ductal dysplasias and hyperplastic alveolar nodule outgrowths were recovered from carcinogen-treated mice. Pituitary isografting enhanced the recovery of ductal dysplasia. Five serially transplanted dysplastic outgrowth lines were established and are their fifty and sixth transplant generations. The data demonstrate that transformed mammary gland cells can be removed from carcinogen-treated mice by means of cell dissociation and transplantation.

High estrogen and low progestin receptor levels in outgrowths of hypophyseal isografts.

Markedly enlarged pituitary isografts in mice contain high concentrations of estrogen receptors and low concentrations, if any, of progestin receptor. This finding is consistent with previous observations that estrogen increases the isograft growth and prolactin secretion while progestin does not. Both types of evidence indicate that in this model system estrogens act indirectly on mammary tumorigenesis by enhancing prolactin secretion in the pituitary isograft and perhaps also the hypophysis in situ, whereas progesterone acts directly on the mammary gland itself.

Inhibition of prolactin-induced mammary cancer in C3Hf (XVII) mice with the trans isomer of bromotriphenylethylene.

C3Hf (XVII) mice never develop spontaneous mammary tumors. However, the transplantation of an isologous pituitary gland under their kidney capsule is followed by a 10-fold increase in serum and pituitary prolactin content (180 ng/ml and 20 micrograms/mg of tissue, respectively), concomitant with an increase of prolactin receptors in mammary glands. Under these conditions, mammary tumors appear in 90% of the mice. If a racemic brominated triphenylethylene, i.e., broparestrol, is administered, serum and pituitary prolactin decrease rapidly (10 ng/ml and 4 micrograms/mg of tissue, respectively), and prolactin receptors in the mammary gland are markedly reduced. This compound also inhibits the development of normal mammary glands, prevents mammary carcinogenesis, and unexpectedly causes a significant atrophy of the ovaries. Our study confirms that prolactin is a key hormone involved in murine mammary carcinogenesis and that it can act directly on the mammary gland by stimulaing the level of its own receptor.

Adrenal regulation of mammary tumorigenesis in female Sprague-Dawley rats: histopathology of mammary tumors.

Mammary tumors induced in female Sprague-Dawley rats by feeding 7,12-dimethylbenz(a)anthracene (DMBA; 20 mg/100 g body weight) were classified according to histological criteria of tissue differentiation, cellular atypia, and evidence of invasion. The 549 tumors could be placed in three categories, nodular hyperplasia, nodular hyperplasia with atypia, and carcinoma, and combinations of all three. Although tumors classified histologically as carcinomas did not metastasize, upon transplantation to the kidney capsule, a tumor classified as a carcinoma grew for eight generations and metastasized. Tumor heterogeneity was a common finding in DMBA-initiated tumors. Carcinomas were an early lesion. As the length of time between DMBA treatment and sacrifice increased, more tumors with areas of carcinoma were found. Therefore, DMBA-initiated tumors progressed to carcinomas either soon after initiation or later by development within nodular hyperplasias. In 4 separate groups of animals (74 adrenalectomized rats and 90 intact rats), postinitiation adrenalectomy increased the numbers of carcinomas compared to intact animals. This effect was consistently seen in the cervical and thoracic mammary glands. We propose that the mechanism for enhancement of progression to greater malignancy by adrenalectomy may be inhibition of differentiation of initiated cells in the absence of glucocorticoids.