Interrelationship between estrogen and thyroxine on the release of luteinizing hormone and gonadotropin-releasing hormone in vitro

Wang, P. S.; Chao, Hsiang‐Tai; Wang, Shyi-Wu

doi:10.1016/0022-4731(87)90399-2

Cited by 5 publications

(3 citation statements)

References 24 publications

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“…The resulsts of our studies are generally not comparable to the scarce data obtained from studies of other authors, who have used various methods for hormonal induction of PCO syndrome in animals. However, when one recognises that our results show no differences in hormone levels in comparison to control, our data are in agreement with the observations of Simard et al (1987) but are opposite to some findings of Ota et al (1986), Lee et al (1986), Bogovich (1991), Bruni et al (1975 and Wang et al (1987). The proper interpretation of these insignificant deviations in estimated hormone levels is difficult and needs further study to evaluate the presented model of PCO induction in hypothyroid rats and to investigate the pathophysiology of this disorder.…”

Section: Discussionsupporting

confidence: 83%

Ovarian LH/hCG receptors and plasma level of LH,17-ß estradiol and progesterone in gonadotropin — induced PCO syndrome in rats

Fitko¹,

Szlezyngier²,

Gajewska³

et al. 2009

Exp Clin Endocrinol Diabetes

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The aim of this work was to investigate the morphologic changes, LH/hCG receptor content in the ovaries and plasma levels of LH, progesterone and estradiol of hypo--and hyperthyroid rats injected with PMSG and hCG. The hypothyroid state was induced by thyreoidectomy (Tr-X) and the hyperthyroid condition by injections of 40 micrograms L-thyroxine daily during 21 days (T4). Gonadotropins were injected during 14 days in daily doses: PMSG--5 i.u. and hCG--10 i.u. The following 8 groups (n = 10-20) were established: control (euthyroid, no treatment), Tr-X, PMSG + hCG, Tr-X + hCG, Tr-X + PMSG, Tr-X + PMSG + hCG, T4 and T4 + PMSG. At the end of experiments rats were sacrificed, ovaries weighed, macroscopically inspected and concentration of LH/hCG receptors was estimated. In blood plasma the level of LH, progesterone and 17-beta estradiol was also analysed. The experiments showed that injections of PMSG alone, or PMSG + hCG in eu-or hypothyroid rats, appear the most effective in induction of PCO syndrome in rats. Low levels of thyroid hormones sensitized the ovaries to gonadotropin action, but a hyperthyroid status diminished or inhibited this response. Thyroid function is also essential in production of LH/hCG receptors in the ovaries. In hypothyroid animals the amount of these receptors was greatly increased, while in hyperthyroid animals they decreased. The level of plasma LH, progesterone, and estradiol showed insignificantly differences and various inconsiderable deviations from norm. These differences were not dependent on large doses of gonadotropins, altered thyroid function, or on cystic or luteinizing changes in the ovary.

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Section: Discussionsupporting

confidence: 83%

Ovarian LH/hCG receptors and plasma level of LH,17-ß estradiol and progesterone in gonadotropin — induced PCO syndrome in rats

Fitko¹,

Szlezyngier²,

Gajewska³

et al. 2009

Exp Clin Endocrinol Diabetes

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“…The concentration of LH and GnRH in plasma a n d /o r media sam ples was determined by RIA as described previously [12,13], using anti-LH serum PW 11-2 and anti-GnRH serum CRR 11B52, respec tively. The antiserum CRR 11B52 was generously provided by Dr. Y.F.…”

Section: Ria Fo R Lh and Gnrhmentioning

confidence: 99%

Age-Related Differences in the Release of Luteinizing Hormone and Gonadotropin-Releasing Hormone in Ovariectomized Rats

Hwang

Pu²,

Hwang³

et al. 1990

Neuroendocrinology

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The effect of aging on the release of gonadotropin-releasing hormone (GnRH) in vitro and of luteinizing hormone (LH) both in vivo and in vitro in ovariectomized (Ovx) rats was studied. Old (21–24 months) and young (3–4 months) rats were Ovx before use. They were injected subcutaneously with estradiol benzoate (25 µg/kg) or sesame oil for 3 days and then challenged with GnRH (0.5,2 or 10 µg/kg) via a jugular catheter. Blood samples were collected immediately before and at 5, 10, 20, 40 and 60 min following GnRH injection. For in vitro study, Ovx rats were decapitated. The anterior pituitary glands (APs) were incubated with GnRH (0.1 or 10 nM) and estradiol (0, 0.1, 1 or 10 nM) at 37 ^¤C for 30 min. The mediobasal hypothalamus was superfused with Locke’s solution at 37 °C for 210 min, and stimulated with 60 mM KCl at 90 and 150 min. The medium samples were collected at 10-min intervals. Concentrations of GnRH and LH in plasma and medium samples were measured by radioimmunoassay. In all rats, the basal and GnRH-stimulated levels of plasma LH were lower in old than in young rats. The spontaneous release of LH in vitro from APs of Ovx rats was increased by aging, whereas GnRH-stimulated release of LH in vitro was lower in old than in young animals. The potassium-stimulated, but not spontaneous, release of GnRH was lower in old than in young Ovx rats. These results suggest that the reduction of plasma LH level in female rats during aging is in part due to a decrease in the K⁺-stimulated release of GnRH, and a reduction of pituitary responsiveness to GnRH and estradiol.

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“…The Ovx-Tx rats were injected subcutaneously with saline or T4 (20 pg/kg b.w./ day), and sesame oil or estradiol benzoate (EB, 0.5 gg/kg b.w./day) once daily for 2 weeks before use. The sham Tx animals were injected with saline and oil [ 10].…”

Section: Animalsmentioning

confidence: 99%

Interrelationship between Thyroxine and Estradiol on the Secretion of Thyrotropin-Releasing Hormone and Dopamine into Hypophysial Portal Blood in Ovariectomized-Thyroidectomized Rats

Wang¹,

Huang²,

Tung³

et al. 1994

Neuroendocrinology

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Effects of thyroxine (T₄) on the secretion of thyrotropin-releasing hormone (TRH) and catecholamines into hypophysial portal blood and on the concentrations of arterial plasma thyroid-stimulating hormone (TSH) and prolactin (PRL) in ovariectomized and thyroidectomized (Ovx-Tx) rats were studied. Immediately after ovariectomy, rats were Tx or sham Tx. The Ovx-Tx rats were injected subcutaneously with estradiol benzoate (EB, 0.5 µg/kg b.w.) or sesame oil, and T₄ (20 µg/kg b.w.) or saline once daily for 2 weeks. The Ovx rats with intact thyroid gland were injected with saline and oil only. The hypophysial portal blood samples were collected and mixed with or without 2, 3-dimercaptopropanol before extraction by methanol or perchloric acid, respectively. The femoral arterial blood was also collected. The concentrations of TRH in methanol-extracted portal plasma and that of TSH and PRL in arterial plasma were measured by radioimmunoassay. The concentrations of catecholamines in perchloric acid-extracted portal plasma samples were measured by radioenzymatic assay. Thyroidectomy in Ovx rats resulted in an increase in portal plasma TRH and arterial plasma TSH. Despite the presence or absence of estradiol, T₄ replacement in Ovx-Tx rats decreased portal plasma TRH and arterial plasma TSH to euthyroid levels. Combination of the injection of T₄and EB in vivo caused significantly decreased levels of portal plasma dopamine and increased arterial plasma PRL compared with those in vehicle-injected Ovx-Tx animals. Concentrations of neither norepinephrine nor epinephrine in hypophysial portal plasma paralleled the altered concentrations of PRL or TSH in arterial plasma. These findings indicate that the negative feedback control of thyroid hormones on the secretion of pituitary TSH is due, at least in part, to inhibition of secretion of TRH into hypophysial portal blood, and that thyroxine potentiates the stimulatory effect of estradiol on the secretion of pituitary PRL by inhibition of secretion of dopamine into hypophysial portal blood.

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Interrelationship between estrogen and thyroxine on the release of luteinizing hormone and gonadotropin-releasing hormone in vitro

Cited by 5 publications

References 24 publications

Ovarian LH/hCG receptors and plasma level of LH,17-ß estradiol and progesterone in gonadotropin — induced PCO syndrome in rats

Ovarian LH/hCG receptors and plasma level of LH,17-ß estradiol and progesterone in gonadotropin — induced PCO syndrome in rats

Age-Related Differences in the Release of Luteinizing Hormone and Gonadotropin-Releasing Hormone in Ovariectomized Rats

Interrelationship between Thyroxine and Estradiol on the Secretion of Thyrotropin-Releasing Hormone and Dopamine into Hypophysial Portal Blood in Ovariectomized-Thyroidectomized Rats

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