Further Findings on the Inhibitory Effect of Estradiol Benzoate on the Circulation and on 45Ca and 3H-proline Incorporation in Rat Bones

Pretreatment of ovarian cells with concanavalin A and wheat-germ agglutinin blocked the gonadotropin-induced cyclic AMP and progesterone responses and this effect was time- and concentration-dependent. Basal production of either cyclic AMP or progesterone, however, was not affected by treatment of cells with lectin. The effect of concanavalin A on gonadotropin-mediated cyclic AMP and progesterone responses was blocked by alpha-methyl D-mannoside and alpha-methyl d-glucoside. Similarly the inhibitory effect of wheat-germ agglutinin was reversed by N-acetyl-D-glucosamine. Pretreatment of ovarian cells with concanavalin A or wheat-germ agglutinin had no effect on protein synthesis in the ovary as monitored by [3H]proline incorporation studies. Concanavalin A and wheat-germ agglutinin did not affect steroid production in response to dibutyryl cyclic AMP and 8-bromo cyclic AMP, indicating that the inhibitory action of lectin was occurring at a step before cyclic AMP formation. Lectins specific for L-fucose, D-galactose and N-acetyl-D-galactosamine, gorse seed agglutinin, peanut agglutinin and Dolichos biflorus agglutinin respectively, did not interfere with gonadotropin-induced cyclic AMP and progesterone responses. The present studies suggest that gonadotropin receptors may be glycoprotein in nature or closely associated with glycoprotein structures with the carbohydrate chain containing N-acetyl-D-glucosamine, mannose and possibly N-acetylneuraminic acid.

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Effects of ovarian hormones on brain opioid binding sites in castrated female rats

AJP Endocrinology and Metabolism ◽

10.1152/ajpendo.1992.263.3.e507 ◽

1992 ◽

Vol 263 (3) ◽

pp. E507-E511 ◽

Cited By ~ 2

Author(s):

D. Dondi ◽

P. Limonta ◽

R. Maggi ◽

F. Piva

Keyword(s):

Negative Feedback ◽

Positive Feedback ◽

Binding Sites ◽

Serum Levels ◽

Estradiol Benzoate ◽

Inhibitory Effect ◽

Feedback Effect ◽

Female Rats ◽

Opioid Binding ◽

Positive Feedback Effect

These experiments were performed to analyze whether treatments of ovariectomized female rats with ovarian steroid regimens able to induce either an increase (positive feedback effect) or a decrease (negative feedback effect) of serum levels of luteinizing hormone (LH) have some impact on the characteristics of mu-opioid binding sites in circumscribed areas of the brain. The increase of serum levels of LH elicited by a treatment with estradiol benzoate (EB) plus progesterone (P; positive feedback effect) was accompanied by a significant decrease in the number of mu-binding sites in the hypothalamus and in the corpus striatum. The decrease in serum levels of LH induced by a treatment with EB alone (negative feedback effect) brought about a significant increase of the number of mu-binding sites in the thalamus and in the hippocampus. These results seem to suggest that the release of LH induced by EB plus P may involve a decrease of hypothalamic mu-binding sites. Apparently, the inhibitory effect on LH release exerted by EB alone does not involve any change of the density of these binding sites in the hypothalamus.

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Systemic and local regulation of oxytocin receptors in the rat uterus, and their functional significance

Canadian Journal of Biochemistry and Cell Biology ◽

10.1139/o83-077 ◽

1983 ◽

Vol 61 (7) ◽

pp. 615-624 ◽

Cited By ~ 23

Author(s):

A.-R. Fuchs ◽

S. Periyasamy ◽

M. S. Soloff

Keyword(s):

Spontaneous Activity ◽

Estradiol Benzoate ◽

Inhibitory Effect ◽

Oxytocin Receptor ◽

Oxytocin Receptors ◽

Partial Correlations ◽

Near Term ◽

Nuclear Estrogen Receptor ◽

The Right ◽

Intact Rats

Rats were made unilaterally pregnant by tying the right oviduct on the day after mating, to compare the oxytocin receptor concentrations in a nondistended, nonpregnant uterine horn with those in a distended, pregnant horn. On day 20, they were subjected to bilateral ovariectomy and indwelling balloons were inserted into both uterine horns. Following ovariectomy, the rats were injected im with either oil, estradiol benzoate (5 μg/rat per 24 h), progesterone (5 mg/rat per 24 h), or estradiol and progesterone together. For comparison, intact rats were studied on days 21 and 22, 24 and 48 h after insertion of the indwelling balloons. Spontaneous uterine activity and the response to increasing amounts of oxytocin were recorded 20–24 h and 44–48 h after surgery, following which the uteri were excised and assayed for oxytocin and estrogen receptors. The oxytocin receptor concentrations in the two horns were different on day 20 before the treatments were begun, the distended pregnant horn having a higher concentration per milligram DNA than the nonpregnant horn. The various treatments always changed the oxytocin receptor concentrations in the same direction; estrogen increased and progesterone inhibited the estrogen-induced rise in oxytocin receptor concentrations. In intact rats, the distention-induced increase in oxytocin receptor concentrations present on day 20 disappeared near term, but in the absence of the ovaries distention of the uterus had a significant influence on the myometrial oxytocin receptor concentrations, potentiating the effect of estrogen. Progesterone selectively inhibited the distention-induced increase in oxytocin receptor concentrations without inhibiting the hypertrophic effect of distention in general. A good correlation between oxytocin receptor numbers and tissue responsiveness was observed in all instances. The changes in spontaneous activity induced by the various treatments were distinct from the changes in oxytocin responsiveness. Estrogen exerted a strong inhibitory action on the activity stimulated by hormone withdrawal, while progesterone had no inhibitory effect. The pregnant distended horn always showed more spontaneous activity than the nonpregnant horn. There was an overall significant correlation between nuclear estrogen receptor and oxytocin receptor concentrations per milligram DNA, although the partial correlations were not significant in all groups (oil and progesterone). It is concluded that ovarian hormones exert the major regulatory influence on myometrial oxytocin receptor concentrations, but other factors including distention modulate their effect.

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Estradiol increases glucagon's satiating potency in ovariectomized rats

AJP Regulatory Integrative and Comparative Physiology ◽

10.1152/ajpregu.2001.281.4.r1290 ◽

2001 ◽

Vol 281 (4) ◽

pp. R1290-R1294 ◽

Cited By ~ 27

Author(s):

Nori Geary ◽

Lori Asarian

Keyword(s):

Signaling Pathway ◽

Food Access ◽

Estradiol Benzoate ◽

Inhibitory Effect ◽

Sesame Oil ◽

Female Rats ◽

Ovariectomized Rats ◽

Hepatic Portal Vein ◽

Hepatic Portal

Estradiol decreases meal size, food intake, and body weight in female rats. To investigate whether these effects of estradiol involve a change in the sensitivity of the signaling pathway through which pancreatic glucagon released during meals contributes to meal termination (satiation), glucagon or glucagon antibodies were infused via the hepatic portal vein in ovariectomized rats that were chronically treated with estradiol benzoate (2 μg/day sc) or vehicle alone (100 μl sesame oil). Infusions began at 1 h after dark onset, as rats were refed after 7 h of food deprivation. Glucagon (3 μg/min for 30 min) decreased feeding during the initial 45 min of food access in both groups of rats, but the inhibition was significantly greater in estradiol- than in oil-treated rats. Similarly, antagonism of endogenous glucagon by infusion of glucagon antibodies (a dose neutralizing 3 ng of glucagon in vitro during the first 3 min of refeeding) increased feeding significantly more in estradiol- than in oil-treated rats. These data indicate that an increase in the activity of the endogenous glucagon satiation-signaling pathway may be part of the mechanism for estradiol's inhibitory effect on feeding.

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Effect of progesterone on plasma luteinizing hormone activity

American Journal of Physiology-Legacy Content ◽

10.1152/ajplegacy.1962.202.4.601 ◽

1962 ◽

Vol 202 (4) ◽

pp. 601-604 ◽

Cited By ~ 32

Author(s):

S. M. McCann

Keyword(s):

Luteinizing Hormone ◽

Marked Decrease ◽

Estradiol Benzoate ◽

Inhibitory Effect ◽

Rat Plasma ◽

Ovariectomized Rats ◽

Ovariectomized Rat ◽

Hormone Activity ◽

Subcutaneous Injections ◽

Plasma Pretreatment

The luteinizing hormone (LH) activity of ovariectomized rat plasma was estimated by the ovarian ascorbic acid depletion technique. A single subcutaneous injection of 25 mg of progesterone produced a slight decrease in this LH activity which was first demonstrable 2 days after injection of progesterone. If a second injection of 25 mg of progesterone was given 2 days after the first, a marked decrease in LH activity was found on testing a day later. Three daily subcutaneous injections of 5 mg of progesterone failed to significantly depress the LH activity in ovariectomized rat plasma. Pretreatment of these ovariectomized rats with estradiol benzoate rendered them more sensitive to the effects of progesterone in that 4 mg progesterone/day was then able to significantly depress the LH activity in their plasma. It was concluded that progesterone alone has a feeble inhibitory effect on the secretion of LH but that estrogen pretreatment sensitizes the animal to this inhibitory action of progesterone.

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Estradiol and its membrane-impermeable conjugate estradiol–BSA inhibit tamoxifen-stimulated prolactin secretion in incubated rat pituitaries

Reproduction ◽

10.1530/rep.1.00807 ◽

2006 ◽

Vol 131 (4) ◽

pp. 763-769 ◽

Cited By ~ 5

Author(s):

R Aguilar ◽

C Bellido ◽

J C Garrido-Gracia ◽

R Alonso ◽

J E Sánchez-Criado

Keyword(s):

Incubation Medium ◽

Estradiol Benzoate ◽

Inhibitory Effect ◽

Prolactin Secretion ◽

Type I ◽

Receptor Modulator ◽

Ovx Rats ◽

Rat Pituitary ◽

Releasing Effect ◽

Membrane Recognition

In the absence of estrogen (E), the selective E receptor modulator tamoxifen (TX) has two agonist effects in the rat pituitary: induction of progesterone receptor (PR)-dependent GnRH self-priming in the gonadotrope, and stimulation of prolactin (PRL) secretion in the lactotrope. TX-induced gonadotropin (GnRH) self-priming is absent when 10−8M estradiol-17β (E2) is added to the incubation medium of pituitaries from TX-treated rats. The present experiments investigated whether PR-independent PRL release into the incubation medium of pituitaries from TX-treated ovariectomized (OVX) rats was affected by E2, and the effect of different ER ligands (ICI182780, TX, estradiol-17α, E2–BSA) on TX-stimulated PRL secretion. Moreover, the effect of E2on TRH-stimulated PRL secretion in pituitaries collected from estradiol benzoate- and TX-treated OVX rats was studied. It was found that: i) incubation with E2supressed the PRL releasing effect of injected TX; ii) whereas coincubation with the pure anti-E type II ICI182780 antagonized the inhibitory effect of E2, coincubation with the anti-E type I TX did not; iii) estradiol-17α lacked inhibitory action, whereas a dose-dependent inhibitory effect of both E2and E2–BSA was noticed; and iv) TRH stimulatory effect on PRL release in pituitaries from TX-treated rats was blocked by addition of E2to the medium. Taken together, these data argue in favor of the presence of specific membrane recognition sites for E in the lactotrope involved in steroid-specific E2inhibition of TX-stimulated PRL secretion.

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Regulatory influence of relaxin on human cervical and uterine connective tissue

Acta Endocrinologica ◽

10.1530/acta.0.1060127 ◽

1984 ◽

Vol 106 (1) ◽

pp. 127-132 ◽

Cited By ~ 19

Author(s):

Ingrid Wiqvist ◽

Anders Norström ◽

Elizabeth O'Byrne ◽

Nils Wiqvist

Keyword(s):

Amino Acid Uptake ◽

Inhibitory Effect ◽

Lower Uterine Segment ◽

Prostaglandin E ◽

Similar Response ◽

Acid Uptake ◽

Experimental Conditions ◽

Inverse Effect ◽

Proline Incorporation

Abstract. Cervical tissue was obtained from women undergoing legal abortion in the 7th–15th week of gestation and tissue from the lower uterine segment was excised at elective Casearean section in the 38th–40th week. The specimens were incubated with [3H]proline in the presence of relaxin or prostaglandin E2 (PGE2). Relaxin had a concentration related inhibitory effect on the radiolabelling in the 7th–9th week but failed to influence the amino acid uptake in the 10th–15th week of pregnancy. PGE2 had the inverse effect, i.e. no influence in the former group but reduced incorporation of proline in the latter group of patients. Incubation of tissue from the lower uterine segment showed a similar response as that of the early pregnant cervix. It is concluded that relaxin has a significant influence on [3H]proline incorporation by cervical and uterine tissue under in vitro experimental conditions.

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No Evidence That RFamide-Related Peptide 3 Directly Modulates LH Secretion in the Ewe

Endocrinology ◽

10.1210/en.2015-1854 ◽

2016 ◽

Vol 157 (4) ◽

pp. 1566-1575 ◽

Cited By ~ 26

Author(s):

C. Decourt ◽

K. Anger ◽

V. Robert ◽

D. Lomet ◽

J. Bartzen-Sprauer ◽

...

Keyword(s):

Receptor Antagonist ◽

Estradiol Benzoate ◽

Inhibitory Effect ◽

Minor Role ◽

Gonadotropin Secretion ◽

Related Peptide ◽

Lh Pulsatility ◽

Lh Release ◽

A Minor ◽

Lh Secretion

Abstract The neuropeptide RFamide-related peptide 3 (RFRP-3) has been implicated in the control of gonadotropin secretion in both birds and mammals. However, in mammals, depending on species, sex and photoperiod, inhibitory, excitatory, or no effect of RFRP-3 on the plasma concentration of LH has been reported. In the ewe, treatment with RFRP-3 either reduced LH concentration or had no effect, and treatment with an RFRP-3 receptor antagonist (ie, RF9) resulted in increased concentration of plasma LH. To clarify these conflicting results in the present study, a set of experiments was performed in ewes. Multiple iv injections of RFRP-3 (6 × 50 μg) in ovariectomized ewes had no effect on plasma LH pulsatility. In intact ewes a bolus injection (500 μg) or an injection (250, 500, or 1000 μg) followed by a 4-hour perfusion (250, 500, or 1000 μg · h−1) of RFRP-3 had no effect on the LH pulse induced by kisspeptin (6.5 μg). In ovariectomized, estrogen-replaced ewes, the LH surge induced by estradiol benzoate was not modified by a 24-hour perfusion of RFRP-3 (500 μg h−1). Finally, although treatment with RF9 induced a robust release of LH, treatment with a more selective RFRP-3 receptor antagonist, GJ14, resulted in no evident increase of LH. In contrast to the inhibitory effect previously suggested, our data are more consistent with the concept that RFRP-3 has no direct effect on LH secretion in ewes and that RF9 effect on LH release is likely not RFRP-3 receptor mediated. Hence, RFRP-3 probably has a minor role on the control of LH secretion in the ewe.

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Modification of Pineal Ultrastructure by Exogenous Hormones

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100060866 ◽

1967 ◽

Vol 25 ◽

pp. 170-171

Author(s):

R. A. Turner ◽

A. E. Rodin ◽

D. K. Roberts

Keyword(s):

Electron Microscopy ◽

Endoplasmic Reticulum ◽

Rough Endoplasmic Reticulum ◽

Estradiol Benzoate ◽

Female Rats ◽

List Type ◽

Type Number ◽

Pregnant Rats ◽

Gonadal Atrophy ◽

Pineal Ultrastructure

There have been many reports which establish a relationship between the pineal and sexual structures, including gonadal hypertrophy after pinealectomy, and gonadal atrophy after injection of pineal homogenates or of melatonin. In order to further delineate this relationship the pineals from 5 groups of female rats were studied by electron microscopy:ControlsPregnant ratsAfter 4 weekly injections of 0.1 mg. estradiol benzoate.After 8 daily injections of 150 mcgm. melatonin (pineal hormone).After 8 daily injections of 3 mg. serotonin (melatonin precursor).No ultrastructural differences were evident between the control, and the pregnancy and melatonin groups. However, the estradiol injected animals exhibited a marked increase in the amount and size of rough endoplasmic reticulum within the pineal cells.

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