Regulation of myometrial beta 2-adrenergic receptors by progesterone and estradiol-17 beta in late pregnant rats

Rat myometrium exhibited a marked decrease in the concentration of beta 2-adrenergic receptors immediately before parturition, i.e., in the last 6 h of pregnancy. This phenomenon continued until the withdrawal of myometrial progesterone (-94% from Day 18 of pregnancy to term) and coincided with the sharp increase (+200%) of the myometrial concentration of estradiol. A linear positive correlation was found (r2 = 0.645) between the concentration of beta 2-adrenergic receptors and the log ratio of myometrial concentration of progesterone/myometrial concentration of estradiol (P/E2), suggesting a modulation of beta 2-adrenergic receptors by steroids. In rats with estrogen-dominated uteri (intact of ovariectomized late pregnant rats injected with estradiol), there was no change either in concentration or affinity of beta 2-adrenergic receptors relative to untreated control pregnant rats. In contrast, rats with progesterone-dominated uteri (intact or ovariectomized late pregnant rats treated with progesterone or ovariectomized rats) have an increased number of beta 2-adrenergic receptors, with a decreased affinity of these receptors compared to untreated control pregnant rats or to estrogen-treated rats. These results suggest that progesterone regulates the number of beta 2-adrenergic receptors in myometrium of late pregnant rats. The mechanisms by which progesterone exerts this regulation remains to be elucidated.     

Progesterone stimulates running wheel activity in adrenalectomized-ovariectomized rats.

Daily treatment with progesterone (5 mg) increased running wheel activity, food intake, and body weight of adrenalectomized-ovariectomized rats. These effects of progesterone are quite similar to those of various corticosteroid treatments in adrenalectomized rats reported previously. In addition, the activity-stimulating action of progesterone is just the opposite of its effect in intact and estradiol-primed ovariectomized rats. These observations are consistent with the hypothesis that the principal role of progesterone in the regulation of body weight is to antagonize the actions of estradiol and that the actions of excessive doses of progesterone in adrenalectomized-ovariectomized rats are simply a by-product of its corticosteroidlike, health-promoting properties.     

The influence of estrogen on plasma prolactin levels induced by thyrotrophin releasing hormone (IRH), clonidine and serotonin in ovariectomized rats.

Prolactin levels were determined in the plasma of ovariectomized and ovariectomized estrogen treated rats by RIA following intraarterial injection of TRH, (1 and 10 μg/rat), clonidine (5 mg/kg) and serotonin (10 mg/kg). In ovariectomized rats, TRH had no effect on plasma prolactin whereas serotonin and clonidine induced slight and moderate increases respectively. In contrast, TRH induced a significant increase in plasma prolactin in estrogen-treated rats while the effects of the other two agents were enhanced only slightly (clonidine) or very markedly (serotonin). These results indicate that the prolactin-releasing activity of TRH is dependent on estrogen and that estrogen differentially affects noradrenergic and serotonergic components of the neuroendocrine mechanism that controls prolactin. It is also suggested that clonidine and serotonin probably do not increase plasma prolactin by releasing endogenous TRH.     

Effect of adrenalectomy and 5-hydroxytryptophan on phasic release of luteinizing hormone

The effect of 5-hydroxytryptophan (5-HTP) on serum progesterone and the possible role of adrenal progesterone in mediating stimulation by 5-HTP of phasic release of luteinizing. hormone (LH) were investigated in estradiol benzoate (EB)-treated ovariectomized rats. LH surges were induced in long-term (at least two weeks) ovariectomized rats by two injections of EB (20 micrograms/rat, s.c.) with an interval of 72 hrs. Administration of 5-HTP (50 mg/kg, i.p.) at 1000 hr in EB-treated ovariectomized rats resulted in a four-fold increase in serum progesterone within 30 mins, and significantly stimulated the LH surge at 1600 hr. This facilitative effect of 5-HTP on serum LH, but not progesterone, was further potentiated in rats pretreated with P-chlorophenylalanine (PCPA) 72 hrs earlier. Adrenalectomy shortly before 5-HTP administration attenuated the LH surge in saline treated controls, and completely blocked the facilitative effect of 5-HTP on the afternoon surge of LH in rats pretreated with PCPA 72 hrs earlier. On the other hand, chronic adrenalectomy (for 6 days) followed by hydrocortisone (0.2 mg/rat/day) replacement not only had no effect on the LH surge in saline treated controls, but also failed to prevent 5-HTP from facilitating the LH surge in PCPA pretreated rats. On the first day of bleeding, the basal LH value at 1000 hr in sham operated controls was significantly suppressed by PCPA pretreatment 48 hrs earlier. The second dose of 5-HTP administered on the next day failed to potentiate LH surges in either sham operated or adrenalectomized rats.(ABSTRACT TRUNCATED AT 250 WORDS)     

A role for the androgen receptor in the endometrial antiproliferative effects of progesterone antagonists

In women and nonhuman primates, treatment with progesterone antagonists suppresses estrogen-dependent mitotic activity in the endometrial glands. This antiproliferative effect is paradoxical, because progesterone antagonists do not bind to the estrogen receptor (ER). While this phenomenon has been termed a "functional noncompetitive antiestrogenic effect," it does not occur in all species or in all regions of the primate reproductive tract, so is best referred to as an "endometrial antiproliferative effect." Recent studies of ours in both women and macaques revealed that the endometrial androgen receptor (AR) was increased by progesterone antagonist treatment. Because androgens are known to suppress estrogen-dependent endometrial proliferation, we hypothesized that the AR was involved in the antiproliferative effects induced by progesterone antagonists. In a test of this hypothesis, we administered the antiandrogen, flutamide, along with progesterone antagonists to ovariectomized, estrogen-treated macaques. Flutamide counteracted the suppressive effects of the progesterone antagonists on endometrial wet weight, thickness, stromal compaction, and mitotic index. Hyaline degeneration of the spiral arteries was also blocked by flutamide. These data implicate the AR as a functional component of the mechanism through which progesterone antagonists induce endometrial antiproliferative effects in the presence of estrogens.     

Role of estrogen in modulating EDHF-mediated dilations in the female rat middle cerebral artery

We tested the hypothesis that endothelium-derived hyperpolarizing factor (EDHF) plays a less dominant role in the female cerebrovasculature. The contribution of EDHF to the ATP-mediated dilation was determined in middle cerebral arteries (MCAs) isolated from male and female rats. Four groups of rats were tested: intact male (n = 12), intact female (n = 13), estrogen-treated ovariectomized female (n = 13), and vehicle-treated ovariectomized female (n = 20) rats. Maximal dilation to ATP was similar in all groups. However, in the presence of N(omega)-nitro-L-arginine methyl ester (L-NAME, 3 x 10(-5) M) and indomethacin (10(-5) M), the maximal dilation to ATP was significantly reduced in intact female (24 +/- 9%) and estrogen-treated ovariectomized female (29 +/- 9%) rats compared with intact male (95 +/- 4%) and vehicle-treated ovariectomized female (96 +/- 2%) rats. The ATP-mediated dilation in L-NAME- and indomethacin-treated MCAs isolated from male and ovariectomized female rats was inhibited by charybdotoxin (10(-7) M), an inhibitor of large-conductance Ca2+-sensitive K+ channels. We have defined EDHF as the L-NAME- and indomethacin-insensitive component of the ATP-mediated dilation. Our findings indicate that EDHF-mediated dilations are negligible in the female rat MCA; these dilations can be significantly enhanced after ovariectomy, suggesting that this effect is mediated by estrogen.     

Influence of estrogen on glutathione levels and glutathione-metabolizing enzymes in uteri and R3230AC mammary tumors of rats

The glutathione content and the activities of several enzymes in its metabolism, glutathione reductase, glutathione peroxidase and γ-glutamyl transpeptidase, were assayed in uteri obtained from estrogen-treated rats and in R3230AC mammary adenocarcinomas obtained from ovariectomized, intact and estrogen-treated hosts. Normal mammary glands, obtained 10–12 days post-partum, were also examined for these parameters.A daily pharmacological dose of 0.4 μg of estradiol-17β induced a maximal increase in uterine weight and in reduced glutathione (GSH); higher doses of estrogen did not significantly increase either of these parameters. Levels of oxidized glutathione (GSSG) were comparable in both estrogen-treated and untreated rats. The time course of the estrogen-induced uterotrophic response was associated with increases in glutathione reductase, glutathione peroxidase and γ-glutamyl transpeptidase activities with the increased GSH level preceding the increase in uterine weight. Compared to neoplasms from intact or ovariectomized animals, tumors from estrogen-treated hosts exhibited significant decreases in levels of GSSG and GSH, as well as in glutathione reductase and glutathione peroxidase activities, but demonstrated a significant elevation of γ-glutamyl transpeptidase activity. Normal glands from lactating rats had decreased GSH levels, lower activities of glutathione reductase and glutathione peroxidase, but elevated γ-glutamyl transpeptidase activity versus tumors from intact rats. Tumors from estrogen-treated rats more closely resembled mammary glands during lactation. The divergent growth responses elicited by estrogen in the uterus and mammary tumor are correlated with the observed changes in GSH levels and enzymes involved in glutathione metabolism.     

Fetal viability and fetal growth after prolonged uterine contractions induced by progesterone withdrawal in late pregnancy in rats.

The hypothesis that sustained uterine contractile activity is the direct cause of fetal death after progesterone withdrawal in late pregnancy in rats was investigated. Pregnant rats were subjected to progesterone withdrawal on day 15 of pregnancy by injecting 2 mg mifepristone (RU 486) kg-1 or by ovariectomy with oestradiol replacement (200 ng day-1). Uterine contractile activity (force and frequency) at 4 h, but not at 2 h, in rats injected with mifepristone was significantly higher than in rats injected with vehicle. The contractile activity in mifepristone-treated rats remained higher than in control rats, at 12, 24 and 48 h. Fetal viability 36 h after mifepristone injection, when uterine contractions had lasted for 32 h, was not significantly different from fetal viability in rats injected with vehicle, but at 42 h after mifepristone injection, fetal viability was significantly reduced. In ovariectomized rats, uterine contractile activity at 12, 24, 36 and 48 h, but not at 8 h, was significantly greater than in ovariectomized rats with progesterone replacement (4 mg day-1). Fetal viability at 42 h after the operation, when uterine contractions had lasted for 30 h, was not significantly reduced, but it was significantly reduced at 48 h. When ovariectomized rats had been left to develop uterine contractions for a period before progesterone was injected, deprivation of progesterone and prolonged uterine contractions for about 30 h did not reduce fetal viability or fetal growth determined on day 18, but it did so 3 days later, on day 21. Administration of 5 mg isoxuprine kg-1 twice a day, which suppressed uterine contractions, improved fetal viability in ovariectomized rats at the earlier stage, but not at the later stage. Nevertheless, isoxuprine did improve fetal growth at the later stage in these ovariectomized rats. It is concluded that increased uterine contractile activity sustained for 32 h or less does not reduce fetal viability, but longer periods of contraction may be the cause of fetal death.     

Size heterogeneity of pituitary and plasma prolactin: Effect of chronic estrogen treatment

Pituitary homogenates and plasma from untreated and estrogen treated ovariectomized rats were subjected to gel filtration chromatography and the prolactin in fractions collected between the void and total elution volumes of the columns was determined by radio- immunoassay. Three components of prolactin, identified as “void volume”, “big” and “little” according to increasing elution volumes, were observed in pituitary homogenates of ovariectomized rats. These three components accounted for 4, 11 and 85% of the total prolactin activity respectively. Estrogen treatment of ovariectomized rats increased the total prolactin in the pituitary and also selectively increased the “big” component to 21% of the prolactin activity on the column. A smaller increase was also observed in the “void volume” component. Gel filtration of the plasma obtained from estrogen-treated rats before and during the estrogen-induced afternoon surge of prolactin showed that “little” prolactin was the predominate form being secreted and that the “void volume” and “big” components were also released. The release of the components was not in proportion to that observed in the pituitary and the larger components were released in a nonuniform manner. The “void volume” component appeared in the plasma as the surge began but then disappeared as the “big” component appeared at the peak of the surge. The big component decreased as the surge waned leaving primarily “little” component in plasma. The data indicate (1) that estrogen stimulates the formation of the larger components of prolactin in the pituitary (2) that the types of prolactin released into plasma of estrogen-treated ovariectomized rats is not in proportion to that found in the pituitary and (3) that the heterogeneous forms of prolactin are selectively released into plasma during the prolonged secretory episode of the afternoon surge of prolactin induced by estrogen.     

Idazoxan inhibits hyperprolactinaemia in ovariectomized estrogen-treated rats

The alpha 2-antagonist idazoxan (IDZ) has previously been shown to inhibit hyperprolactinaemia triggered by various stimuli such as lactation, stress, serotonergic agents and morphine (Preziosi, Martire, Navarra, Pistritto and Vacca 1989; Krulich, Jurcovicova and Le 1989). In this study, we investigated the PRL-lowering activity of IDZ in ovariectomized estrogen-treated (OET) rats; since a PRL surge usually occurs in normal cycling rats on the day of proestrus, the effect of IDZ on pulsatile PRL release in intact female rats was also studied. IDZ significantly lowered plasma PRL levels in OET rats; no elevated PRL values were observed in normal cycling rats, indicating that IDZ might inhibit PRL surges in these animals. It is concluded that IDZ is an effective PRL-lowering agent in a number of physiological and pharmacological hyperprolactinaemic models.     

Role of ovarian steroid hormones in the regulation of adenylate cyclase during early progestation

The hormonal regulation of uterine adenylate cyclase (AC) was measured in the rat by radiochemical analysis. Animals made pseudopregnant by cervical stimulation were ovariectomized on Day 1 (the first appearance of leukocytes in the vaginal smear) and injected for 6 days with sesame oil, 0.1-10.0 micrograms estrone, 2.0 mg progesterone, or 1.0 microgram estrone + 2.0 mg progesterone. AC activity in ovariectomized controls remained at basal levels (2.8-3.3 pmol cAMP formed/min X mg protein). The injection of progesterone did not alter AC activity significantly, but estrone increased AC activity during Days 3-5, and the response (5-17 pmol) was dose dependent. The action of estrone was not inhibited by progesterone. The present experiments revealed: a) AC from estrone-treated rats was activated 2- to 4-fold by 10 mM NaF; b) following treatment with estrone + progesterone, AC was activated 2- to 3-fold by a trauma to the uterus; c) unlike the response to fluoride, the effect of trauma was temporally limited to Day 4; and d) when AC was activated by trauma, no further increase was elicited by NaF. The data indicated that the transient sensitivity of AC to activation by trauma on Day 4 in E+P-treated rats was identical to that in intact rats and paralleled the normal timing of uterine sensitivity to decidual induction.     

Size homogeneity of plasma prolactin in the female rat following various natural, pharmacological and stressful stimuli

Gel filtration on Sephadex G-150 was performed on freshly drawn plasma from ovariectomized, estrogen-treated rats following 10 minutes of ether inhalation, intraperitoneal administration of TRH (1 μg/rat) or pimozide (500 μg/kg body weight) and at the peak of the estrogen-induced afternoon surge of prolactin (1700 h). Plasma from intact lactating rats 30 minutes after suckling was also subjected to gel filtration. For comparison, homogenates of fresh and frozen pituitaries from ovariectomized, estrogen-treated rats were chromatographed. Prolactin activity was determined by RIA in each fraction eluted between the void and total volumes of the column. Immunoreactive prolactin in plasma following all experimental procedures eluted as a single component with a K_av of approximately 0.6. Chromatography of the fresh pituitary homogenate showed prolactin immunoactivity at the void volume and at a K_av of 0.4 and 0.6. A homogenate of frozen pituitary contained a component with a K_av of 0.3 in addition to those seen in fresh pituitary. These studies demonstrate that although the rat pituitary contains multiple molecular forms of immuno-reactive prolactin, only one small component is found in plasma.     

Effect of ovariectomy and replacement therapy on the tissue lipid pattern in rats.

Ovariectomy increases the percentage of total lipids in liver, kidney and uterus of intact cyclic rats. Estrogen and progesterone, when administered individually to ovariectomized rats, caused a decrease in the total lipid content of all tissues. Th effect of progesterone in estrogen-primed rats is not significant. Triglyceride and cholesterol content increases after ovariectomy; treatment with estrogen in ovariectomized rats led to a decrease in the concentration of these lipids. Progesterone has no significant effect on these lipids but showed an antagonistic action when given in estrogen-primed ovariectomized rats. The proportions of ethanolamine, choline and inositol phospholipids decreased after spaying and increased when estrogen was given to spayed rats. Progesterone alone had effect only on the uterus whereas progesterone administered to estrogen-primed rats showed an antagonistic effect in all tissues.     

Changes in CD38 expression and ADP-ribosyl cyclase activity in rat myometrium during pregnancy: influence of sex steroid hormones

Cyclic ADP-ribose (cADPR), synthesized by CD38, regulates intracellular calcium in uterine smooth muscle. CD38 is a transmembrane protein that has both ADP-ribosyl cyclase and cADPR hydrolase enzyme activities involved in cADPR metabolism. CD38 expression and its enzyme activities in uterine smooth muscle are regulated by estrogen. In the present study, we examined CD38 expression, its enzyme activities, and cADPR levels in myometrium obtained from rats at 14-17 days of gestation (preterm) and at parturition (term). CD38 expression, ADP-ribosyl cyclase activity, and cADPR levels were higher in uterine tissues obtained from term rats compared with that of preterm rats, while activity of cADPR hydrolase did not significantly change. In an effort to address whether changes in estrogen: progesterone ratio that occur during pregnancy account for the observed effects on CD38 expression and function, we determined the effect of different doses of progesterone in the presence of estrogen on CD38 expression and its enzyme activities in uterine smooth muscle obtained from ovariectomized rats. In myometrium obtained from ovariectomized rats, estrogen administration caused increased CD38 protein expression and ADP-ribosyl cyclase activity. The estrogen-induced increases in CD38 expression and ADP-ribosyl cyclase activity were inhibited by simultaneous administration of 10 or 20 mg of progesterone. These results indicate that the estrogen:progesterone ratio determines CD38 expression and ADP-ribosyl cyclase activity. These changes in CD38/cADPR pathway may contribute to increased uterine motility and onset of labor.     

Estrogen replacement stimulates fatty acid oxidation and impairs post-ischemic recovery of hearts from ovariectomized female rats

Women less than 50 years of age, the majority of whom are likely premenopausal and exposed to estrogen, are at greater risk of a poor short-term recovery after myocardial ischemia than men and older women. Since estrogen enhances non-cardiac lipid utilization and increased lipid utilization is associated with poor post-ischemic heart function, we determined the effect of estrogen replacement on post-ischemic myocardial function and fatty acid oxidation. Female Sprague-Dawley rats, either intact (n = 15) or ovariectomized and treated with 17beta-estradiol (0.1 mg x kg(-1) x day(-1), s.c., n = 14) or corn oil vehicle (n = 16) for 5 weeks, were compared. Function and fatty acid oxidation of isolated working hearts perfused with 1.2 mM [9,10-3H]palmitate, 5.5 mM glucose, 0.5 mM lactate, and 100 mU/L insulin were measured before and after global no-flow ischemia. Only 36% of hearts from estrogen-treated rats recovered after ischemia compared with 56% from vehicle-treated rats (p > 0.05, not significant), while 93% of hearts from intact rats recovered (p < 0.05). Relative to pre-ischemic values, post-ischemic function of estrogen-treated hearts (26.3 +/- 10.1%) was significantly lower than vehicle-treated hearts (53.4 +/- 11.8%, p < 0.05) and hearts from intact rats (81.9 +/- 7.0%, p < 0.05). Following ischemia, fatty acid oxidation was greater in estrogen-treated hearts than in the other groups. Thus, estrogen replacement stimulates fatty acid oxidation and impairs post-ischemic recovery of isolated working hearts from ovariectomized female rats.     

Estrogen supplement prevents the calcium hypersensitivity of cardiac myofilaments in ovariectomized rats

Our previous biochemical and mechanical studies have demonstrated an increase in Ca2+ sensitivity of cardiac myofilaments in ovariectomized rats. To test whether the body weight gain associated with ovariectomy contributed some effects to the changes in myofibrillar functions, the relations of pCa (-log Ca2+ molar concentration) to actomyosin adenosine triphosphatase (ATPase) activity of isolated myofibrillar preparations from 10-week pair-fed ovariectomized rats were compared with those from sham-operated controls. Despite similar body weights, the maximum myofibrillar ATPase activity was significantly lower in pair-fed ovariectomized rats as compared to that of sham-operated controls. In addition, the pCa-actomyosin ATPase relationship of pair-fed ovariectomized hearts still demonstrated a significant leftward shift in pCa50 (-log half-maximally Ca2+ activation) from that of sham-operated controls. To find out which hormone was responsible for the observed increase in myofibrillar Ca2+ sensitivity, different sex hormone supplemental regimens were administered to ovariectomized rats. Subcutaneous injection of estrogen (5 microg/rat) or estrogen plus progesterone (1 mg/rat) three times a week could effectively prevent the changes in body weight, heart weight, and uterine weight of the ovariectomized animals. Moreover, supplements of either estrogen or progesterone could prevent a decrease in maximum ATPase activity. In contrast, only the estrogen replacement could abolish the Ca2+ hypersensitivity of the myofilaments in these ovariectomized rats. These results suggest differential cardio-regulatory effects of ovarian sex hormones on the Ca2+ activation of the myofilaments.     

17beta-estradiol prevents oxidative stress and decreases blood pressure in ovariectomized rats

In this study, we tested whether estrogen deficiency is associated with oxidative stress and decreased nitric oxide (NO) production, which could be responsible for an increased blood pressure in ovariectomized rats. Hemodynamic studies were performed on conscious, chronically instrumented rats. Chronic estrogen replacement on ovariectomized rats lowered blood pressure approximately 13 mmHg, from 119 +/- 3 mmHg in ovariectomized rats to 106 +/- 3 mmHg in ovariectomized-treated rats; it was also accompanied by an increase in cardiac index and vascular conductance, achieving hemodynamic values similar to those shown by sham-operated rats. N(G)-nitro-L-arginine methyl ester administration lowered significantly less the vascular conductance (0.14 +/- 0.01 vs. 0.22 +/- 0.03 and 0.26 +/- 0.01 ml. min(-1). mmHg(-1)/100 g; P < 0.05) in ovariectomized rats than in the sham-operated and estrogen-treated ovariectomized rats, respectively. Estrogen replacement prevented the lower plasma levels of nitrites/nitrates observed in ovariectomized rats. The lower plasma total antioxidant status and reduced thiol groups and the increase in plasma lipoperoxides presented in ovariectomized animals were reestablished with the estrogen treatment. These results show that estrogen administration decreases blood pressure and increases vascular conductance in ovariectomized rats. This effect may be related to an increase in NO synthesis and/or preventing oxidative stress, then improving endothelial function.     

Inhibitory effects of the antiprogestin, RU 486, on progesterone actions and luteinizing hormone secretion in pituitary gonadotrophs

The effects of RU 486 on the modulation of LH release by progesterone were investigated in cultured anterior pituitary cells from ovariectomized adult female rats. The inhibitory effect of progesterone on LH secretion was demonstrable in estrogen-treated pituitary cells, in which addition of 10(-6) M progesterone to cells cultured in the presence of 10(-9) M estradiol for 52 h reduced the LH response to GnRH (10(-11) to 10(-7) M). When RU 486 was superimposed upon such combined treatment with estradiol and progesterone, the suppressive effect of progesterone on GnRH-induced LH release was completely abolished. The converse (facilitatory) effect of progesterone on LH secretion was observed in pituitary cells pretreated with 10(-9) M estradiol for 48 h and then with 10(-6) M progesterone for 4 h. When RU 486 was added together with progesterone during the 4 h treatment period, the facilitatory effect of progesterone was blocked and LH release fell to below the corresponding control value. The direct effect of RU 486 on LH secretion in the absence of exogenous progesterone was evaluated in cells cultured in the absence or presence of 10(-9) M estradiol and then treated for 4 to 24 h with increasing concentrations of RU 486 (10(-12) to 10(-5) M) and stimulated with GnRH (10(-9) M) during the last 3 h of incubation. In estrogen-deficient cultures, 4 h exposure to RU 486 concentrations of 10(-6) M and above decreased the LH response to GnRH by up to 50%. In cultures pretreated with 10(-9) M estradiol, GnRH-stimulated LH responses was inhibited by much lower RU 486 concentrations, of 10(-9) M and above. After 24 h of incubation the effects of RU 486 were similar in control and estradiol-pretreated pituitary cell cultures. Thus, RU 486 alone has a significant inhibitory effect on LH secretion that is enhanced in the presence of estrogen. The antiprogestin is also a potent antagonist of both the inhibitory and the facilitatory actions of progesterone upon pituitary gonadotropin release in vitro.     

Ultrastructure of neurons in the ventromedial nucleus or the hypothalamus in ovariectomized rats with or without estrogen treatment

Summary The fine structure of the ventrolateral and dorsomedial subdivisions of the ventromedial nucleus (VMN) of the hypothalamus was examined in ovariectomized/control and ovariectomized/estrogen-treated rats to compare neurons of these areas to other neurons (specifically the ventrolateral thalamus), and to determine the effects of estrogen on these cells. The neurons of the VMN contain a large nucleus with a prominent nucleolus, rough endoplasmic reticulum (RER), polysomes, a Golgi complex, coated, uncoated and dense-cored vesicles, lysosome-like bodies, inclusion bodies, multivesicular bodies, whorl bodies and myelin figures. Similar organelles were present in the neurons of the ventrolateral thalamus, although polysomes were more prominent, and the cells lacked dense-cored vesicles in the perikarya. Differences in the cells of the VMN between ovariectomized/control and ovariectomized/estrogen-treated rats included a more conspicuous stacking of the RER and greater number of dense-cored vesicles in the estrogen-treated group in both the ventrolateral and dorsomedial subdivisions. In both areas the differences were statistically significant, although more marked in the ventrolateral subdivision. In both VMN subdivisions, the increased stacking of the RER could be correlated with the greater number of dense-cored vesicles and may reflect increased biosynthesis of a secretory product.Supported by grants from the National Institutes of Health (1 R01 NS15889-01) to R.S.C. and (HD-05751) to D.W.P.     

The influence of estradiol and progesterone and melatonin supplementation on TNF-alpha levels in ovariectomized and pinealectomized rats

The aim of this study was to investigate the effect of estradiol and progesterone and melatonin supplementation on TNF-alpha levels in ovariectomized and pinealectomized rats. The study was carried out on 42 adult, Spraque-Dawley strain female rats aged 6 months and weighing 200-250 grams. The rats were divided into 6 groups, each group contained 7 rats. Group 1: Sham-ovariectomized (Sham-Ovx), Group 2: Ovariectomized (Ovx), Group 3: Ovx and estradiol (E) and progesterone (P) supplemented (Ovx+E-P) group, Group 4: Ovx+E-P+Melatonin (M) supplemented group, Group 5: Ovx Pinealectomized (Pnx) group, Group 6: Ovx - Pnx+E-P supplemented group. Serum TNF-alpha levels were determined after 4 weeks application period. Group 6 (Ovx-Pnx+E-P) has the highest serum TNF-alpha compared with other groups while group 2 (ovariectomized), has the lowest levels (P<0.001). Group 5 was higher than groups 1, 2, 3 and 4 (P <0.001). The results of the study show that ovariectomy reduces the serum level of TNF-alpha, but estradiol and progesterone application prevents this reduction in ovariectomized rats. However, pinealectomy intensifies the increases in TNF-alpha levels in ovariectomized and estradiol and progesterone supplemented rats, whereas melatonin reduces TNF-alpha levels in ovariectomized rats.