Morphological and functional changes in pituitary-thyroid axis following prolonged exposure of female rats to constant light

Abstract Light regulates numerous physiological functions including secretion of different hormones. Our aim was to determine morphological and functional changes of the pituitary growth hormone (GH) and prolactin (PRL) producing cells in female rats exposed to constant light regime from the peripubertal to adult period of life. Starting from the thirtieth postnatal day, female Wistar rats were exposed to constant light (600 lx) for the following 95 days. Controls were maintained under the regular laboratory lighting conditions. The GH and PRL cells were immunohistochemically visualized. Changes in cell volumes and volume densities were evaluated by stereology. Concentrations of PRL and GH in circulation were also determined. We detected significant decrease of the GH cell volume and volume density, followed by reduced the GH blood concentration in comparison to the controls. In contrast, PRL cells were larger in size and their volume density was significantly increased when compared to the controls. Accordingly, PRL concentration was elevated. It can be concluded that exposure of female rats to constant light regime, from peripubertal to adult period of life, causes inhibition of the pituitary GH and stimulation of PRL cells.

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Neonatal exposure to bisphenol A alters the hypothalamic-pituitary-thyroid axis in female rats

Toxicology Letters ◽

10.1016/j.toxlet.2017.12.029 ◽

2018 ◽

Vol 285 ◽

pp. 81-86 ◽

Cited By ~ 17

Author(s):

Marina O. Fernandez ◽

Nadia S. Bourguignon ◽

Paula Arocena ◽

Matías Rosa ◽

Carlos Libertun ◽

...

Keyword(s):

Bisphenol A ◽

Female Rats ◽

Neonatal Exposure ◽

Pituitary Thyroid Axis ◽

Thyroid Axis

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Effects of oestradiol benzoate on the pituitary-thyroid axis of male and female rats

Acta Endocrinologica ◽

10.1530/acta.0.1020386 ◽

1983 ◽

Vol 102 (3) ◽

pp. 386-391 ◽

Cited By ~ 10

Author(s):

Rubén Boado ◽

Edgardo Ulloa ◽

Angel A. Zaninovich

Keyword(s):

Corn Oil ◽

Plasma Concentrations ◽

Female Rats ◽

Moderate Degree ◽

Male And Female ◽

Male And Female Rats ◽

Oestradiol Benzoate ◽

Pituitary Thyroid Axis ◽

Thyroid Axis ◽

Thyroid Gland Activity

Abstract. In the present work the effects of oestradiol benzoate (EB) on pituitary and plasma concentrations of TSH, plasma T4 and T3, and thyroidal activity of male and female rats have been studied. Wistar rats weighing between 150 to 200 g were injected sc with varying doses of EB in corn oil for 9 or 30 days. The animals were exsanguinated by cardiac puncture and the hypophyses removed and individually homogenized at 4°C in 200 μl PBS buffer. Pituitary and plasma TSH were measured by radioimmunoassay. Thyroidal activity was evaluated by a 4 h 131I uptake and by 48 h thyroidal release plasma slopes derived form the ratio PB[125I] (from thyroidal secretion) to PB[131I] (from exogenous [131I]T4). In both male and female rats the 10 and 25 μg doses of EB produced a significant decrease in pituitary TSH content; this effect was more pronounced when the 25 μg dose was given over 30 days. Plasma T4 decreased significantly; plasma T3 was moderately elevated in all groups (NS) and significantly increased in female rats treated with 25 μg EB (P < 0.01). It is concluded that EB induced a marked depression of intrapituitary TSH, probably due to a decrease in synthesis, without affecting the release of TSH into the circulation. Moreover, EB accelerated peripheral T4 kinetics and thyroid gland activity, albeit to a moderate degree.

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Effects of long-term food reduction on the hypothalamus-pituitary-thyroid axis in male and female rats

Journal of Endocrinology ◽

10.1677/joe.0.1500169 ◽

1996 ◽

Vol 150 (2) ◽

pp. 169-178 ◽

Cited By ~ 42

Author(s):

G A C van Haasteren ◽

E Linkels ◽

H van Toor ◽

W Klootwijk ◽

E Kaptein ◽

...

Keyword(s):

Binding Capacity ◽

Mrna Translation ◽

Female Rats ◽

Short Term ◽

Male And Female ◽

Corticosterone Secretion ◽

Male And Female Rats ◽

Pituitary Thyroid Axis ◽

Thyroid Axis ◽

Serum Tsh

Abstract The reduced thyroid activity during short-term starvation is associated with a lowered hypothalamic synthesis and secretion of TRH. However, little is known about the cause of the reduced thyroid function during prolonged malnutrition. We have therefore studied the effects of food reduction to one-third of normal (FR33) on the hypothalamus-pituitary-thyroid axis of male and female Wistar rats. After 3 weeks body weights of FR33 rats were almost 50% lower than those of controls. In both sexes, FR33 caused marked increases in serum corticosterone, and decreases in serum TSH, thyroxine (T4), free T4, tri-iodothyronine (T3) and free T3. While the free T3 fraction (FFT3) in serum decreased, the free T4 fraction (FFT4) tended to increase. Electrophoretic analysis indicated that decreased FFT3 was correlated with an increased thyroxine-binding globulin, while the increase in FFT4 seemed due to a decreased thyroxine-binding prealbumin binding capacity. Total RNA and proTRH mRNA in the hypothalamus were not affected by FR33. Median eminence and posterior pituitary TRH content tended to increase in FR33 rats, suggesting that hypothalamic TRH release is reduced in FR33 rats. Anterior pituitary TSH content was decreased by FR33 in both sexes, but pituitary TSHβ mRNA and TRH receptor status were not affected except for increased pituitary TSHβ mRNA in female FR33 rats. Although FR33 had no effect on pituitary weight, pituitary RNA and membrane protein content in FR33 rats were 50–70% lower than values in controls. In conclusion, prolonged food reduction suppresses the pituitary-thyroid axis in rats. In contrast to short-term food deprivation, the mechanism whereby serum TSH is suppressed does not appear to involve decreases in proTRH gene expression, but may include effects on pituitary mRNA translation. Our results further support the hypothesis that TSH release may be lowered by increased corticosterone secretion, although the mechanism of this effect may differ between acute starvation and prolonged food reduction. Journal of Endocrinology (1996) 150, 169–178

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Sequential changes in the pituitary thyroid axis after chronic TRH administration: effects on euthyroid and thyroxine treated female rats

Acta Endocrinologica ◽

10.1530/acta.0.1090237 ◽

1985 ◽

Vol 109 (2) ◽

pp. 237-242 ◽

Cited By ~ 5

Author(s):

R. Iglesias ◽

M. Llobera ◽

E. Montoya

Keyword(s):

Serum Levels ◽

Female Rats ◽

Thyrotrophin Releasing Hormone ◽

Partial Restoration ◽

Pituitary Thyroid Axis ◽

Thyroid Axis ◽

The Times ◽

Transient Elevation ◽

Tsh Levels

Abstract. The effect of chronic oral thyrotrophin-releasing hormone (TRH) administration on thyrotrophin (TSH), l-triiodothyronine (T3) and l-thyroxine (T4) serum levels, pituitary TSH concentration and serum response to acute TRH injection, has been studied in female rats under different thyroidal conditions: shamoperated control animals, and thyroidectomized animals receiving 25 μg l-T4/100 g body weight/day. After 30 days, these groups were divided into two subgroups (6–10 animals per group), one receiving the aforementioned treatment and the other the same plus 2 mg TRH/10 ml distilled water (DW), as drinking water. TRH-treated sham-operated animals showed significantly reduced serum and pituitary TSH levels and inceased serum T3 levels at most of the times studied (1, 6, 10, 18 and 34 days of oral TRH or DW administration), and a transient elevation in serum T4 between day 1 and 6. Thyroidectomized-l-T4-treated animals showed increased serum and pituitary TSH levels throughout the treatment and reduced T3 and T4 serum levels at the beginning, as compared to thyroidectomized-l-T4-treated animals. TSH response to iv TRH administration on the 10th day of oral TRH administration was reduced in controls chronically treated with oral TRH as compared to nontreated controls, and was increased in thyroidectomizedl-T4-treated animals on chronic TRH vs the same group on oral DW. These results suggest that chronic TRH administration can stimulate TRH synthesis in vivo, bypassing the inhibitory effects of thyroid hormones, the increased pituitary TSH reserve being responsible for the partial restoration of a response to acute TRH injection in the thyroidectomized-l-T4-treated animals.

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The environmental contaminant tributyltin leads to abnormalities in different levels of the hypothalamus-pituitary-thyroid axis in female rats

Environmental Pollution ◽

10.1016/j.envpol.2018.06.006 ◽

2018 ◽

Vol 241 ◽

pp. 636-645 ◽

Cited By ~ 9

Author(s):

Marcelle Novaes Andrade ◽

Ana Paula Santos-Silva ◽

Paula Rodrigues-Pereira ◽

Francisca Diana Paiva-Melo ◽

Niedson Correa de Lima Junior ◽

...

Keyword(s):

Environmental Contaminant ◽

Female Rats ◽

Pituitary Thyroid Axis ◽

Thyroid Axis ◽

Different Levels

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Morphological Changes in the Rat Granulosa Cell Surface During Differentiation Induced by Estradiol and Gonadotropins

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100079851 ◽

1977 ◽

Vol 35 ◽

pp. 484-485

Author(s):

P. Bagavandoss ◽

JoAnne S. Richards ◽

A. Rees Midgley

Keyword(s):

Cell Surface ◽

Granulosa Cell ◽

Morphological Changes ◽

Follicular Development ◽

Female Rats ◽

Functional Changes ◽

Group 4 ◽

Group 3 ◽

Group 5 ◽

Group 2

During follicular development in the mammalian ovary, several functional changes occur in the granulosa cells in response to steroid hormones and gonadotropins (1,2). In particular, marked changes in the content of membrane-associated receptors for the gonadotropins have been observed (1).We report here scanning electron microscope observations of morphological changes that occur on the granulosa cell surface in response to the administration of estradiol, human follicle stimulating hormone (hFSH), and human chorionic gonadotropin (hCG).Immature female rats that were hypophysectcmized on day 24 of age were treated in the following manner. Group 1: control groups were injected once a day with 0.1 ml phosphate buffered saline (PBS) for 3 days; group 2: estradiol (1.5 mg/0.2 ml propylene glycol) once a day for 3 days; group 3: estradiol for 3 days followed by 2 days of hFSH (1 μg/0.1 ml) twice daily, group 4: same as in group 3; group 5: same as in group 3 with a final injection of hCG (5 IU/0.1 ml) on the fifth day.

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