Interaction of ovarian steroids and periarterial alpha 1-adrenergic receptors in altering uterine blood flow during the estrous cycle of gilts

Analysis of Uterine Blood Flow in Breeding Sows through the Estrus and Early Diestrus, and after Artificial Insemination

This study aimed to determine uterine blood flow indices by transabdominal Doppler ultrasound in sows (n = 18) under different conditions: (i) sows after estrus detection (day 0, D0); (ii) sows 2 h after artificial insemination (AI), performed 24 h after detection of estrus (day 1, D1); (iii) sows in early diestrus (day 5, D5). Moreover, three different types of seminal doses were used for AI depending on the ejaculate fraction included (F1: doses containing only the rich fraction of the ejaculate; F2: F1 + the transition fraction between rich and poor fractions; F3: F2 and poor fraction). The statistical analysis revealed significant differences in some indices regarding the period of analysis (D0, D1, and D5). Diastolic velocity and mean velocity showed lower values at D5 in comparison with D0 and D1 (p < 0.01). On the other hand, the pulsatility index and the relationship systolic velocity/diastolic velocity indicated higher values at D5 in comparison with D0 and D1 (p < 0.01). No differences were observed regarding the type of seminal dose used in any of the time points analyzed (p > 0.05). Neither insemination per se nor the type of ejaculate fraction used immediately modified the uterine vascularity, but some indices are affected by the stage of the estrus cycle (estrus vs. early diestrus).

Time Series Ovarian Transcriptome Analyses of the Porcine Estrous Cycle Reveals Gene Expression Changes during Steroid Metabolism and Corpus Luteum Development

Simple Summary

The estrous cycle, which is divided into follicular and luteal phases based on ovulation, is influenced by reproductive hormones which affect reproduction and cause changes in the reproductive system of the pig. As the main reproductive organ, the ovary is involved in ovulation and changes in the corpus luteum. We aimed to identify dynamic changes in gene expression through differentially expressed gene profiling and to provide a comprehensive understanding of the molecular mechanisms that occur in the pig ovary during the estrous cycle. The transcriptome analysis revealed that the dynamic change in gene expression was more activated in the luteal phase than in the follicular phase. Functional analysis revealed that the metestrus and diestrus periods are important in preparation for pregnancy or the next estrous cycle after ovulation.

Abstract

The porcine estrous cycle is influenced by reproductive hormones, which affect porcine reproduction and result in physiological changes in the reproductive organs. The ovary is involved in ovulation, luteinization, corpus luteum development, and luteolysis. Here, we aimed to provide a comprehensive understanding of the gene expression patterns in porcine ovarian transcriptomes during the estrous cycle through differentially expressed genes profiling and description of molecular mechanisms. The transcriptomes of porcine ovary were obtained during the estrous cycle at three-day intervals from day 0 to day 18 using RNA-seq. At seven time points of the estrous cycle, 4414 DEG were identified; these were classified into three clusters according to their expression patterns. During the late metestrus and diestrus periods, the expression in cluster 1 increased rapidly, and steroid biosynthesis was significant in the pathway. Cluster 2 gene expression patterns represented the cytokine–cytokine receptor interaction in significant pathways. In cluster 3, the hedgehog signaling pathway was selected as the significant pathway. Our study exhibited dynamic gene expression changes with these three different patterns of cluster 1, 2, and 3. The results helped identify the functions and related significant genes especially during the late metestrus and diestrus periods in the estrous cycle.

Cystathionine γ-lyase promotes estrogen-stimulated uterine artery blood flow via glutathione homeostasis

During pregnancy, estrogen (E₂) stimulates uterine artery blood flow (UBF) by enhancing nitric oxide (NO)-dependent vasodilation. Cystathionine γ-lyase (CSE) promotes vascular NO signaling by producing hydrogen sulfide (H₂S) and by maintaining the ratio of reduced-to-oxidized intracellular glutathione (GSH/GSSG) through l-cysteine production. Because redox homeostasis can influence NO signaling, we hypothesized that CSE mediates E₂ stimulation of UBF by modulating local intracellular cysteine metabolism and GSH/GSSG levels to promote redox homeostasis. Using non-pregnant ovariectomized WT and CSE-null (CSE KO) mice, we performed micro-ultrasound of mouse uterine and renal arteries to assess changes in blood flow upon exogenous E₂ stimulation. We quantified serum and uterine artery NO metabolites (NO_x), serum amino acids, and uterine and renal artery GSH/GSSG. WT and CSE KO mice exhibited similar baseline uterine and renal blood flow. Unlike WT, CSE KO mice did not exhibit expected E₂ stimulation of UBF. Renal blood flow was E₂-insensitive for both genotypes. While serum and uterine artery NO_x were similar between genotypes at baseline, E₂ decreased NO_x in CSE KO serum. Cysteine was also lower in CSE KO serum, while citrulline and homocysteine levels were elevated. E₂ and CSE deletion additively decreased GSH/GSSG in uterine arteries. In contrast, renal artery GSH/GSSG was insensitive to E₂ or CSE deletion. Together, these findings suggest that CSE maintenance of uterine artery GSH/GSSG facilitates nitrergic signaling in uterine arteries and is required for normal E₂ stimulation of UBF. These data have implications for pregnancy pathophysiology and the selective hormone responses of specific vascular beds.

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CSE-null mice exhibit abnormal estrogen augmentation of uterine artery blood flow.

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Estrogen lowers uterine artery nitric oxide metabolites in CSE null mice.

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CSE loss and estrogen additively impair uterine artery glutathione homeostasis.

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Neither CSE loss nor estrogen influences renal artery blood flow or glutathione.

Sympathetic regulation of ovarian functions under chronic estradiol treatment in rats

Activation of the sympathetic nerve to the ovary (superior ovarian nerve: SON) decreases ovarian blood flow and estradiol secretion in rats in the estrous phase. The present study examined the effects of long-term estradiol treatment on the sympathetic regulation of both ovarian blood flow and estradiol secretion. Non-pregnant Wistar rats received sustained subcutaneous estradiol (5μg/day) or saline for 4weeks. Chronic estradiol treatment did not affect ovarian blood flow at rest, while changed the basal ovarian estradiol secretion rate, i.e., narrow ranges (4-34pg/min) in estradiol-treated rats, versus wide ranges (3-192pg/min) in saline-treated rats of different estrous cycles. SON was electrically stimulated at different frequencies (2, 5 and 20Hz). Ovarian blood flow was decreased by SON stimulation in a stimulus frequency-dependent manner in both saline- and estradiol-treated rats, but the threshold was shifted from 2Hz to 5Hz after chronic estradiol treatment. Ovarian estradiol secretion rate was not significantly changed by SON stimulation at any frequency in saline-treated rats, while it was markedly decreased by SON stimulation at high frequencies (5 and 20Hz) in estradiol-treated rats. In conclusion, chronic estradiol treatment augments sympathetic inhibition of ovarian estradiol secretion perhaps by inhibiting the hypothalamic-pituitary-ovarian axis.

Doppler sonographic examination of uterine and placental perfusion in cows in the last month of gestation and effects of epidural anesthesia and isoxsuprine

The massive increase in size of the fetus and uterus in the last trimester is accompanied by an increasing demand for nutrients and oxygen, and it is assumed that this demand is met by increasing uterine and fetal perfusion. The goals of this study were to measure the perfusion of the uterine arteries and the placentomes in the last month of gestation and to investigate the effect of epidural anesthesia and isoxsuprine on perfusion. During the last month of gestation, eight Braunvieh cows underwent nine color Doppler sonographic examinations of the uterine arteries to determine diameter (DM), pulse rate (PR), resistance index, time-averaged maximum blood flow velocity (TAMV), and blood flow volume (BFV), and power-mode Doppler sonography was used to determine perfusion of placentomes. The PR increased (P < 0.001), and the BFV and TAMV of the ipsilateral uterine artery decreased between 4.5 and 0.5 weeks prepartum (BFV, 236.8 ± 65.80 and 208 ± 41.52 cm(3)/s, P < 0.01; TAMV, 140.0 ± 26.53 cm/s and 125.2 ± 18.46 cm/s, P < 0.05). After sonographic examination, the cows received epidural administration of local anesthetic (100-mg lidocaine) in the sacrococcygeal space or isoxsuprine (200 mg/cow, iv), and the sonographic measurements were repeated 30 minutes later. After epidural anesthesia, the TAMV and BFV of the contralateral uterine artery increased by 5.4% (P < 0.05) and 7.9% (P < 0.01). In the placentomes of the gravid uterine horn, the relative placentome perfusion and the color pixel grading (Cp) increased by 10.1% (P < 0.05) and 11.5% (P < 0.01) after epidural anesthesia. After isoxsuprine, the DM, PR, and BFV increased by 4.7%, 49.3%, and 16.9% in the ipsilateral uterine artery and by 10.8%, 48.7%, and 22.8%, respectively in the contralateral uterine artery. The TAMV of the ipsilateral uterine artery increased by 7.1% (P < 0.01), and the resistance index decreased in both uterine arteries (ipsilateral 24.2%, contralateral 14.9%, both P < 0.00001). Isoxsuprine increased the relative placentome perfusion and the Cp of the placentomes by 18.1% and 18.3% in the gravid horn and by 10.2% and 24.2% in the nongravid horn. Blood flow variables changed little in the last month of gestation. However, epidural anesthesia and isoxsuprine caused changes in uterine and placentome perfusion that suggest improvement of placental nutrient and oxygen supply to the fetus.

Hypoxia Represses ER-α Expression and Inhibits Estrogen-Induced Regulation of Ca2+-Activated K+ Channel Activity and Myogenic Tone in Ovine Uterine Arteries: Causal Role of DNA Methylation

Previous in vivo study demonstrated that chronic hypoxia during gestation was associated with estrogen receptor-α (ER-α) gene repression in ovine uterine arteries. Yet, it remains undetermined whether hypoxia had a direct effect and if DNA methylation played a causal role in hypoxia-mediated ER-α gene repression. Thus, this study tested the hypothesis that prolonged hypoxia has a direct effect and increases promoter methylation resulting in ER-α gene repression and inhibition of estrogen-mediated adaptation of uterine vascular tone. Uterine arteries isolated from nonpregnant and pregnant sheep were treated ex vivo with 21.0% O2 and 10.5% O2 for 48 hours. Hypoxia significantly increased ER-α promoter methylation at both specificity protein-1 and upstream stimulatory factor binding sites, decreased specificity protein-1 and upstream stimulatory factor binding to the promoter, and suppressed ER-α expression in uterine arteries of pregnant animals. Of importance, the effects of hypoxia were blocked by a methylation inhibitor 5-aza-2'-deoxycytidine. In addition, hypoxia abrogated steroid hormone-mediated increase in ER-α expression and inhibited the hormone-induced increase in large-conductance Ca(2+)-activated K(+) channel activity and decrease in myogenic tone in uterine arteries of nonpregnant animals, which were reversed by 5-aza-2'-deoxycytidine. The results provide novel evidence of a direct effect of hypoxia on heightened promoter methylation that plays a causal role in ER-α gene repression and ablation of steroid hormone-mediated adaptation of uterine arterial large conductance Ca(2+)-activated K(+) channel activity and myogenic tone in pregnancy.

Effects of estrogen plus progesterone on hemodynamic and vascular reactivity in hypertensive postmenopausal women

AIMS

To investigate the medium-term effects of estrogen plus progesterone therapy (EPT) on vascular reactivity, endothelial function and hemodynamic responses in 20 hypertensive postmenopausal women.

METHODS

This randomized, double-blind, cross-over, placebo-controlled study investigates the effect of 6 months of EPT (conjugated equine estrogen plus medroxyprogesterone). Blood pressure (office and ambulatory), heart rate and heart rate variability (HRV) were measured at baseline and following EPT/placebo treatment. In eight women, we used a wire-myograph to assess endothelial function and contractile response of subcutaneous arteries to transmural nerve stimulation (TNS) and exogenous noradrenaline.

RESULTS

EPT decreased vascular reactivity to cumulative TNS compared with baseline (p<0.01) and placebo (p<0.05). Moreover, EPT diminished sensitivity to exogenous noradrenaline (p<0.05). Although EPT reinforced response to acetylcholine, we observed no difference in maximal relaxation induced by substance P or acetylcholine. EPT did not affect ambulatory blood pressure, heart rate or HRV.

CONCLUSIONS

Oral combined medium-term EPT reduces adrenergic reactivity in subcutaneous arteries from treated hypertensive postmenopausal women. EPT might act postjunctionally at the adrenergic vascular receptor level. In the present study, EPT neither reduces sympathetic activity nor increases vagal tone, and thus does not support an effect on the central hemodynamic system.

Chronic hypoxia inhibits sex steroid hormone-mediated attenuation of ovine uterine arterial myogenic tone in pregnancy

Previous studies in ovine uterine arteries have demonstrated that sex steroid hormones upregulate extracellular signal-regulated kinase 1/2 expression and downregulate the protein kinase C signaling pathway, resulting in the attenuated myogenic tone in pregnancy. The present study tested the hypothesis that chronic hypoxia during gestation inhibits the sex steroid-mediated adaptation of extracellular signal-regulated kinase 1/2 and protein kinase C signaling pathways and increases the myogenic tone of uterine arteries. Uterine arteries were isolated from nonpregnant and near-term pregnant sheep that had been maintained at sea level (≈300 m) or exposed to high-altitude (3801 m) hypoxia for 110 days. In contrast to the previous findings in normoxic animals, 17β-estradiol and progesterone failed to suppress protein kinase C-induced contractions and the pressure-induced myogenic tone in uterine arteries from hypoxic animals. Western analyses showed that the sex steroids lost their effects on extracellular signal-regulated kinase 1/2 expression and phospho- extracellular signal-regulated kinase 1/2 levels, as well as the activation of protein kinase C isozymes in uterine arteries of hypoxic ewes. In normoxic animals, pregnancy and the sex steroid treatments significantly increased uterine artery estrogen receptor-α and progesterone receptor B expression. Chronic hypoxia selectively downregulated estrogen receptor-α expression in uterine arteries of pregnant animals and eliminated the upregulation of estrogen receptor-α in pregnancy or by the steroid treatments observed in normoxic animals. The results demonstrate that, in the ovine uterine artery, chronic hypoxia in pregnancy inhibits the sex steroid hormone-mediated adaptation of decreased myogenic tone by downregulating estrogen receptor-α expression, providing a mechanism linking hypoxia and maladaptation of uteroplacental circulation and an increased risk of preeclampsia in pregnancy.

The influence of steroids on vascular tension of isolated superficial veins of the nose and face during the estrous cycle of gilts

The arrangement of the superficial facial veins enables blood flow from the nasal cavity into the peripheral circulation by two pathways: through the frontal vein into the cavernous sinus and through the facial vein into the external jugular vein. The current study was designed to determine whether estradiol and progesterone affect the vascular tone of the superficial veins of the nose and face in cycling gilts (Sus scrofa f. domestica) and to analyze the immunolocalization of progesterone receptors and estradiol receptors in these veins. The influence of hormones on vascular tension differed depending on the type of vessel and the phase of the estrous cycle. Estradiol decreased vascular tension in the nasal vein during the follicular phase (P<0.05) and increased tension in the frontal vein during the luteal phase (P<0.05). Progesterone increased the vascular tension of the frontal vein (P<0.05) and decreased the tension of the other veins (P<0.05) in both phases of the cycle. Expression of estradiol receptor beta but not of progesterone receptor was observed in the superficial veins of the nose and face. In conclusion, the effect of ovarian steroid hormones on the vascular tension of the superficial veins of the nose and face in female pigs as well as the reactivity of these veins to steroid boar pheromones can affect the blood supply from the nasal cavity to the venous cavernous sinus. We propose that the ovarian steroid hormones that modulate the vascular tension of the nasal and facial veins may also influence the action of boar pheromones absorbed into the nasal mucosa in gilts and may reach the brain via local destination transfer.

Direct chronic effect of steroid hormones in attenuating uterine arterial myogenic tone: role of protein kinase c/extracellular signal-regulated kinase 1/2

Pregnancy is associated with a significant decrease in uterine vascular tone and an increase in uterine blood flow. The present study tested the hypothesis that estrogen and progesterone differentially regulate the extracellular signal-regulated kinase (ERK)1/2 and protein kinase C (PKC) signaling pathways in vascular smooth muscle, resulting in a decrease in uterine vascular myogenic tone in pregnancy. Uterine arteries were isolated from nonpregnant and near-term pregnant sheep. Chronic treatment (48 hours) of nonpregnant uterine arteries with 17beta-estradiol and progesterone caused a significant decrease in PKC-mediated contractions and pressure-induced myogenic tone. In accordance, treatment of near-term pregnant uterine arteries for 48 hours with ICI 182780 and RU 486 significantly increased PKC-induced contractions and myogenic tone. In contrast, acute treatment for 30 minutes had no effect on uterine artery contractility. An ERK1/2 inhibitor, PD098059, restored the chronic effect of steroids on PKC-mediated contractions in nonpregnant sheep. ERK1/2 protein and mRNA levels were greater in near-term pregnant as compared with nonpregnant uterine arteries. 17beta-Estradiol and progesterone increased ERK1/2 protein in nonpregnant sheep. In agreement, ICI 182780 and RU 486 caused significant decreases in ERK1/2 protein in near-term pregnant sheep. Western blot showed 6 PKC isozymes, alpha, beta(I), beta(II), delta, epsilon, and zeta, in the uterine arteries. 17beta-Estradiol and progesterone decreased the particulate:cytosolic ratios of PKCalpha, epsilon, and zeta, respectively, in nonpregnant sheep. ICI 182780 and RU 486 increased the ratios in near-term pregnant sheep. The results indicate a direct chronic effect of the steroid hormones in the upregulation of ERK1/2 expression and downregulation of the PKC signaling pathway, resulting in attenuated myogenic tone of the uterine artery in pregnancy.

Review article: steroid hormones and uterine vascular adaptation to pregnancy

Pregnancy is a physiological state that involves a significant decrease in uterine vascular tone and an increase in uterine blood flow, which is mediated in part by steroid hormones, including estrogen, progesterone, and cortisol. Previous studies have demonstrated the involvement of these hormones in the regulation of uterine artery contractility through signaling pathways specific to the endothelium and the vascular smooth muscle. Alterations in endothelial nitric oxide synthase expression and activity, nitric oxide production, and expression of enzymes involved in PGI(2) production contribute to the uterine artery endothelium-specific responses. Steroid hormones also have an effect on calcium-activated potassium channel activity, PKC signaling pathway and myogenic tone, and alterations in pharmacomechanical coupling in the uterine artery smooth muscle. This review addresses current understanding of the molecular mechanisms by which steroid hormones including estrogen, progesterone, and cortisol modulate uterine artery contractility to alter uterine blood flow during pregnancy with an emphasis on the pregnant ewe model.

Color Doppler sonographic analysis of uterine and ovarian artery blood flow in women with polycystic ovary syndrome

PURPOSE

To study the blood flow patterns of utero-ovarian circulation in polycystic ovary syndrome (PCOS) and to assess their relationship with clinical, metabolic, and hormonal data.

METHODS

Forty-three women with PCOS and 43 age-matched healthy controls underwent Doppler examination of the utero-ovarian circulation in the follicular phase. Demographic, hormonal, and metabolic parameters were determined. Student's t-test, chi(2)-test, and Spearman correlation test were used for statistical analysis.

RESULTS

The ovarian artery pulsatility index (PI), resistance index (RI), and SD ratios were significantly lower in PCOS than in controls on the right side (p < 0.001, p = 0.02, p = 0.001, respectively) as well as on the left side (p < 0.001, p < 0.001, p < 0.001, respectively). The uterine artery systolic/diastolic (S/D) ratio was higher on both sides (p = 0.01) and the PI was higher on the left side (p = 0.02) in PCOS than in controls. The right uterine artery PI was positively correlated with luteinizing hormone and hemoglobin (r = 0.417, p = 0.043; r = 0.427, p = 0.033, respectively), the right uterine artery S/D was positively correlated with body mass index (r = 0.479, p = 0.015), and the left uterine artery PI was positively correlated with insulin (r = 0.458, p = 0.021).

CONCLUSION

Doppler sonography of the utero-ovarian circulation may contribute to the evaluation of PCOS patients and a better understanding of the pathophysiology of this syndrome.

The oestrous cycle and early pregnancy – a new concept of local endocrine regulation

Facts discovered in recent decades have compelled us to revise long-established views on the physiological regulation of cyclic adjustments to the reproductive system in preparation for pregnancy in females. Evidence has been presented to show that changes in the uterine blood supply induced by the oestrogen/progesterone ratio in the blood and cytokines are important in the regulation of the secretory function of the endometrium. Progressive reduction in uterine blood flow during the luteal phase of the oestrous cycle causes regressive changes in endometrial cells and release of prostaglandin (PG) F(2 alpha), resulting in initiation of luteolysis. Retrograde transfer of PGF(2 alpha) in the area of the mesometrium vasculature is an important element in the mechanism protecting the corpora lutea against luteolysis before day 12 of the porcine oestrous cycle and during early pregnancy and pseudopregnancy. Results of many studies presented in this review indicate that PGF(2 alpha) pulses in uterine venous blood during the follicular phase of the oestrous cycle may not be due to PGF(2 alpha) secretion by endometrial cells, but occur due to remodeling of the endometrium and pulsatile exretion of PGF(2 alpha) in accordance with rhythmic uterine contractions caused by oxytocin.

Adaptation of uterine artery thick- and thin-filament regulatory pathways to pregnancy

Little is known about the adaptation of uterine artery smooth muscle contractile mechanisms to pregnancy. The present study tested the hypothesis that pregnancy differentially regulates thick- and thin-filament regulatory pathways in uterine arteries. Isometric tension, intracellular free Ca(2+) concentration, and phosphorylation of 20-kDa myosin light chain (MLC(20)) were measured simultaneously in uterine arteries isolated from nonpregnant and near-term (140 days gestation) pregnant sheep. Phenylephrine-mediated intracellular free Ca(2+) concentration, MLC(20) phosphorylation, and contraction tension were significantly increased in uterine arteries of pregnant compared with nonpregnant animals. In contrast, phenylephrine-mediated Ca(2+) sensitivity of MLC(20) phosphorylation was decreased in the uterine arteries of pregnant sheep. Simultaneous measurement of phenylephrine-stimulated tension and MLC(20) phosphorylation in the same tissue indicated a decrease in MLC(20) phosphorylation-independent contractions in the uterine arteries of pregnant sheep. In addition, activation of PKC produced significantly lower sustained contractions in uterine arteries of pregnant compared with nonpregnant animals in the absence of changes in MLC(20) phosphorylation levels in either vessels. In uterine arteries of nonpregnant sheep, the mitogen-activated protein kinase kinase/extracellular signal-regulated kinase inhibitor PD-098059 significantly increased phenylephrine-mediated, MLC(20) phosphorylation-independent contractions. The results suggest that in uterine arteries, pregnancy upregulates alpha(1)-adrenoceptor-mediated Ca(2+) mobilization and MLC(20) phosphorylation. In contrast, pregnancy downregulates the Ca(2+) sensitivity of myofilaments, which is mediated by both thick- and thin-filament pathways.

The effect of semen extender, seminal plasma and raw semen on uterine and ovarian blood flow in mares

Transrectal color Doppler sonography was used to evaluate the effect of intrauterine infusion of skim milk semen extender, seminal plasma and raw semen on the endometrium and blood flow in the uterine and ovarian arteries in mares. Six Trotter mares (mean age: 12 years) were examined during estrus in three cycles. Each mare received an intrauterine infusion of 20 ml of skim milk semen extender, seminal plasma or raw semen during estrus in one of three cycles. Blood flow measurements in both uterine and ovarian arteries and the determination of intrauterine fluid via sonography were performed before each infusion and 1, 3, 6, 12, and 24 h after infusion. Forty-eight hours later, the intrauterine infusion and measurements were repeated using the same time intervals. Changes in blood flow were detected using transrectal color Doppler sonography and were evaluated using the mean time-averaged maximum velocity (TAMV) of the blood flow. Cytological and bacteriological examination of uterine swabs performed 48 h after the second infusion revealed less inflammation and bacterial growth in mares infused with skim milk semen extender than in those infused with seminal plasma or raw semen. There was an increase in intrauterine fluid as early as 1 h after infusion of any of the substances. The infusion of skim milk semen extender had no effect on uterine blood flow. Within 1 h after infusion of seminal plasma or raw semen, there was an increase in the TAMV values of both uterine arteries (P<0.05). In contrast, ovarian blood flow increased only in the artery ipsilateral to the preovulatory follicle and only after the infusion of raw semen (P<0.05). In conclusion, the changes in uterine perfusion observed after intrauterine infusion may be associated with endometrial inflammation and vasodilatory components in the seminal plasma, whereas the changes seen in ovarian blood flow are possibly attributable to the interaction between sperm and oviduct.

The vasodepressor effect of androgens in pithed rats: potential role of calcium channels

Estrogens induce vasodilatation and/or hypotension in several experimental models, probably by a blockade of calcium currents. However, very little is known about the potential cardiovascular effects of androgens. We have previously shown that 5 beta-reduced androgens are more potent vasorelaxants than their precursors (delta 4-3 keto), 5-reduced progestins and 17beta-estradiol. The present study set out to investigate if this vasorelaxant effect of 5-reduced androgens is operative in vivo in the analysis of the potential vasodepressor effect of these compounds in vagosympathectomized, pithed rats. After increasing diastolic blood pressure (DBP) by a continuous infusion of norepinephrine (0.059 micromol x kg(-1)min(-1)), i.v. bolus injections of 3 alpha-hydroxy-5 beta-androstan-17-one (etiocholanolone), 5 beta-dihydrotestosterone (5 beta-DHT), and its isomer 5 alpha-dihydrotestosterone (5 alpha-DHT) (5-25 micromol x kg(-1) each) produced, separately, dose-dependent vasodepressor responses. These responses were biphasic: an immediate fall in DBP (reaching the nadir within 1.7 min) was followed by a further slow decrease that reached a maximum between 80 and 100 min after steroid administration. The order of potency of androgens in decreasing DBP was: 5 beta-DHT>5 alpha-DHT=etiocholanolone for the short-lasting response and 5 alpha-DHT>5 beta-DHT>or=etiocholanolone for the longer lasting response. Importantly, the same doses of these compounds produced no significant changes in heart rate. Moreover, 5 beta-DHT significantly antagonized the vasopressor responses to methyl 1,4-dihydro-2,6-dimethyl-3-nitro-4-(2-trifluromethylphenyl)-pyridine-5-carboxylate (Bay K 8644) with a blocking profile similar to that of nifedipine (NIF). This finding suggests that a blockade of voltage-operated calcium channels may be involved in androgen-induced hypotension.

Low-dose estrogen supplementation improves vascular function in hypogonadal men

It is widely accepted that in women, estrogens provide protection against the development of cardiovascular disease. However, the cardiovascular role of estrogens in men remains uncertain, despite preliminary evidence that endogenous estrogens produced by aromatization of androgenic precursors are of physiological importance. Hypogonadal men have very low levels of circulating estrogen. We studied the responsiveness of forearm resistance arteries to vasoconstrictor and vasodilator agents in 12 men (mean+/-SEM age, 68.7+/-2.6 years) rendered hypogonadal as a result of treatment for prostatic cancer, before and after 8 weeks of estrogen supplementation (estradiol valerate 1 mg daily; n=7) or placebo (n=5). Forearm blood flow was measured by venous occlusion plethysmography, and vasoactive agents were infused through a brachial artery cannula in doses that did not affect blood pressure or heart rate. Estrogen supplementation was well tolerated, with no adverse effects. After estrogen treatment, mean estradiol levels increased from <30 to 308+/-65 pmol/L, and both systolic and diastolic blood pressures were reduced. HDL cholesterol levels increased significantly, and vasoconstrictor responses to the NO synthase inhibitor N(G)-monomethyl-L-arginine (1, 2, 4 micromol/min) were enhanced. Vasoconstrictor responses to angiotensin II (8, 16, 32 ng/min) were markedly attenuated by estrogen treatment, as were vasoconstrictor responses to norepinephrine (25, 50, 100 ng/min). Estrogen did not alter the vasodilator responses to acetylcholine (9.25, 18.5, 37 microgram/min) or to the endothelium-independent agent sodium nitroprusside (1.6 microgram/min). Responses to all vasoactive agents were unchanged after administration of placebo. We conclude that low-dose estrogen supplementation in hypogonadal men is well tolerated, lowers blood pressure, and may affect vascular reactivity in a manner that is potentially beneficial, through several mechanisms, including enhancement of basal NO release and attenuation of vasoconstrictor responses to angiotensin II and norepinephrine. These findings suggest the need to consider a possible clinical role for estrogenic compounds in cardiovascular risk reduction in some groups of men.

Sex steroid hormones exert biphasic effects on cytosolic magnesium ions in cerebral vascular smooth muscle cells: possible relationships to migraine frequency in premenstrual syndromes and stroke incidence

Clinically, it is known that: (1) magnesium (Mg) supplementation relieves premenstrual problems (e.g., migraine, bloating and edema) occurring in the late luteal phase of the menstrual cycle; and (2) migraine syndromes, particularly in women, are associated with deficits in brain and serum ionized Mg levels. We investigated whether concentrations of sex steroid hormones, found in the serum during the menstrual cycle of women, are associated with changes in the levels of cytosolic free magnesium ions ([Mg2+]i in single cultured canine cerebral vascular smooth muscle cells. The resting level of [Mg2+]i in these cells was 645 +/- 89 microM before exposure to sex steroid hormones. Exposure of these vascular cells to a low concentration of estrogen (10 pg/ml) failed to interfere with the levels of [Mg2+]i. However, exposure to estrogen, at concentrations ranging from 40 to 200 pg/ml, induced significant loss of [Mg2+]i in a concentration-dependent manner. At a concentration of 200 pg/ml estrogen, the level of [Mg2+]i decreased approximately 30% in comparison with controls. Progesterone produced biphasic effects on the levels of [Mg2+]i, depending on its concentration. Exposure of the cultured cells to a low concentration of progesterone (0.5 ng/ml) resulted in an increased level of [Mg2+]i (from 690 +/- 50 microM to 753 +/- 56 microM, p < 0.05). However, when these cells were exposed to higher concentrations of progesterone (i.e., from 5.0 to 20 ng/ml), the cellular levels of [Mg2+]i were decreased significantly. The higher the estrogen or progesterone concentration, the lower the levels of [Mg2+]i. In contrast, testosterone, a male hormone, didn't produce any significant alteration in [Mg2+]i levels in these cerebral vascular smooth muscle cells. These data indicate that low, physiological concentrations of female sex hormones, estrogen and progesterone, help cerebral vascular smooth cells sustain normal concentrations of [Mg2+]i, which are beneficial to vascular function, whereas high levels of estrogen and progesterone deplete, significantly, [Mg2+]i in cerebral vascular smooth muscle cells, possibly resulting in cerebrovasospasms and reduced cerebral blood flows related to premenstrual syndromes, migraine and stroke risk. Our findings could provide new insight into the mechanism whereby migraine occurs frequently in the late luteal phase in the premenstrual syndrome. In addition, our results demonstrate that female sex steroids but not testosterone (in physiologic concentrations) can exert direct effects on [Mg2+]i in cerebral vascular cells.

Low-dose aspirin treatment improves ovarian responsiveness, uterine and ovarian blood flow velocity, implantation, and pregnancy rates in patients undergoing in vitro fertilization: a prospective, randomized, double-blind placebo-controlled assay

OBJECTIVE

To determine the effects of low-dose aspirin on ovarian response, uterine and ovarian blood flow velocity, and implantation and pregnancy rates in patients undergoing IVF.

DESIGN

Prospective, randomized, double-blind placebo-controlled assay.

SETTING

Department of Reproductive Medicine, CER Medical Institute, Buenos Aires, Argentina.

PATIENT(S)

Two hundred ninety-eight infertile patients (mean [+/- SDI age, 35.6+/-4.09 years) undergoing IVF cycles.

INTERVENTION(S)

In the treatment group, 149 patients underwent controlled ovarian hyperstimulation and received a daily dose of 100 mg of aspirin. In the control group, 149 patients underwent controlled ovarian hyperstimulation in association with placebo.

MAIN OUTCOME MEASURE(S)

Number of follicles, number of oocytes retrieved, serum E2 levels, uterine and ovarian pulsatility index, cancellation rate, number of embryos transferred, and implantation and pregnancy rates.

RESULT(S)

There were statistically significant differences between the treatment group and the control group, respectively, in the number of follicles (19.8+/-7.2 versus 10.2+/-5.3), number of oocytes retrieved (16.2+/-6.7 versus 8.6+/-4.6), serum E2 levels (2,923.8+/-1,023.4 versus 1,614.3+/-791.7 pg/mL), uterine pulsatility index (1.22+/-0.34 versus 1.96+/-0.58), ovarian pulsatility index (1.18+/-0.31 versus 1.99+/-0.56), pregnancy rate (45% versus 28%), and implantation rate (17.8% versus 9.2%).

CONCLUSION(S)

Low-dose aspirin treatment significantly improves ovarian responsiveness, uterine and ovarian blood flow velocity, and implantation and pregnancy rates in IVF patients.

Possible role of Ca2+ channels in the vasodilating effect of 5beta-dihydrotestosterone in rat aorta

It has previously been shown that the androgen, 5beta-dihydrotestosterone (17beta-hydroxy-5beta-androstan-3-one, 5beta-DHT), is able to produce an endothelium-independent vasodilating effect in rat aorta. The present study analyzed the mechanisms underlying the above vasodilator effect of 5beta-dihydrotestosterone, with particular emphasis on verifying a possible interaction with GABA(A) receptors, beta-adrenoceptors and Ca2+ channels. Rat aortic rings without endothelium were isometrically recorded. 5Beta-dihydrotestosterone produced a concentration-dependent relaxation on the contractions induced by noradrenaline (NA; 0.3 microM) or K+ (KCl; 60 mM), with the latter being more sensitive to 5beta-dihydrotestosterone-induced relaxation than the former; the concentration-response curves showed that 5beta-dihydrotestosterone is significantly more potent than 17beta-estradiol(1,3,5(10)-estratrien-3,17beta-diol) to induce vasodilatation. The vasodilating effect of 5beta-dihydrotestosterone on noradrenaline-induced contraction was resistant to blockade by the GABA(A) receptor antagonists, picrotoxin or bicuculline, and the beta-adrenoceptor antagonist, propranolol, a finding that excludes an interaction of the steroid with GABA(A) receptors and beta-adrenoceptors. Interestingly, the contractions evoked by calcium in depolarized tissues were substantially inhibited by 5beta-dihydrotestosterone, implying that this steroid could be an endogenous calcium channel blocker; consistent with this finding, 5beta-dihydrotestosterone was able to relax tissues precontracted with the calcium channel opener, Bay K 8644. Moreover, although the rings precontracted with noradrenaline and potassium were almost equipotently relaxed by 5beta-dihydrotestosterone. Nifedipine was more potent than 5beta-dihydrotestosterone to block the potassium-induced contraction, but the steroid was more effective than nifedipine to prevent noradrenaline-induced contraction. The above results suggest that 5beta-dihydrotestosterone causes relaxation of rat aorta by acting directly on the membrane of smooth muscle cells; this non-genomic action may be explained in terms of a blockade of voltage- and receptor-dependent calcium channels, a mechanism that restricts the availability of extracellular calcium in the contractile machinery.

Estrogen supplementation decreases norepinephrine-induced vasoconstriction and total body norepinephrine spillover in perimenopausal women

Estrogens are reported to provide protection against the development of cardiovascular disease in women, but the mechanisms underlying these effects are not well defined. We hypothesized that estrogen might reduce neural cardiovascular tone. We therefore studied responses to exogenous norepinephrine and norepinephrine spillover in 12 perimenopausal women randomized to 8 weeks of estrogen supplementation (estradiol valerate, 2 mg daily, n=7) or placebo (n=5). Forearm blood flow was measured by venous occlusion plethysmography, and vasoactive agents were infused through a brachial artery cannula in doses that did not influence blood pressure or heart rate. Total body and forearm norepinephrine spillover were measured by radiotracer methodology. Forearm vasoconstrictor responses to norepinephrine (25, 50, and 100 ng/min) were attenuated after estrogen supplementation (P=.002). Vasoconstrictor responses to angiotensin II (8, 16, and 32 ng/min) were unchanged postestrogen. There was a significant reduction in total body spillover of norepinephrine after estrogen supplementation (pre-estrogen, 700+/-152; postestrogen, 439+/-150 ng/min; P<.05), but there was no change after placebo. Total body clearance and forearm spillover of norepinephrine were unchanged by either estrogen or placebo. Estrogen supplementation also significantly decreased both systolic and diastolic blood pressures. Therefore, estrogen supplementation in perimenopausal women selectively attenuates vasoconstrictor responses to norepinephrine and reduces total body norepinephrine spillover, which is an index of sympathetic neural activity.

Involvement of adrenoceptors in the ovarian vascular pedicle in the regulation of counter current transfer of steroid hormones to the arterial blood supplying the oviduct and uterus of pigs

1. On Day 10 of the oestrous cycle in pigs, after laparotomy noradrenaline (NA), methoxamine (alpha 1-adrenomimetic, M), Prazosin (alpha 1-adrenolytic, Pr) in total doses of 4 mumol, and saline were infused (10 min) into the superficial layer of mesovarium on both sides of the ovarian pedicle vasculature, close to the ovary. 2. Blood flow in the ovarian artery, heart rate and progesterone (P4) and androstenedione (A4) secretion from the ovary and their concentrations in the ovarian venous effluent, as well as the concentrations of P4 and A4 in the blood supplying the oviduct and the uterus, were determined. 3. A significant increase of P4 and A4 secretion after NA and M infusion and increased concentrations of P4 and A4 in the ovarian venous effluent were found, but these changes did not influence the counter current transfer of hormones from the venous effluent into arterial blood supplying the oviduct and the uterus. 4. Infusion of Pr caused a significant decrease of P4 and A4 secretion and their concentrations in the ovarian venous effluent and significantly increased A4 concentration in the blood supplying the oviduct and uterus. 5. The results indicate that stimulation of alpha 1-adrenoceptors in the area of ovarian vasculature did not influence, whereas block of alpha 1-adrenoceptors affected, the local concentration of steroid hormones in the blood supplying the oviduct and the part of the uterus proximal to the ovary, despite the changes in the concentrations of steroid hormones in the ovarian effluent.

Pharmacological characterization of alpha 1-adrenoceptors in porcine uterine artery

This study was undertaken to ascertain if changes in the affinity to alpha 1-adrenoceptor agonists and antagonists could explain the increase in uterine artery vasoconstriction to adrenergic stimuli during the luteal phase of the estrous cycle in pigs. We also sought to determine the subtype(s) of adrenoceptor (alpha 1A and alpha 1B) in the porcine uterine artery. When phenylephrine was the agonist, uterine artery pA2 values for prazosin were 8.98, 9.04 and 9.10 in the luteal and follicular phases and in early pregnancy, respectively. The KA (dissociation constant) values for phenylephrine were 6.5, 3.7 and 4.4 (microM) in the luteal and follicular phases and in early pregnancy, respectively. The use of the putative alpha 1A-adrenoceptor WB4101 (2-[[[2-(2,6-dimethoxyphenoxy)ethyl]amino]methyl]-1,4-benzodioxane ) and the alpha 1B-adrenoceptor antagonist chloroethylclonidine indicated that both alpha 1A- and alpha 1B-adrenoceptors are present in the porcine uterine artery and that a similar magnitude of inhibition of responses to noradrenaline by each of the antagonists occurred in arteries from the luteal and follicular phases and in early pregnancy. This suggests that the alpha 1A:alpha 1B adrenoceptor ratio does not vary significantly during the estrous cycle and in early pregnancy. This study indicates that porcine uterine artery alpha 1-adrenoceptor affinity is similar in the luteal and follicular phases of the estrous cycle and in early pregnancy.

Effects of progestogens on haemostasis

Epidemiological data suggested an involvement of the progestogen component in the pathomechanism of venous and arterial diseases during intake of oral contraceptives. The influence of progestogens on haemostasis parameters depend on type and dose of the progestogen, the presence of an estrogen, the route of application, and the duration of use. Treatment of women with progestogen-only preparations caused only minor effects on coagulation and fibrinolysis. Similarly, during hormone replacement therapy with natural estrogens, the additional application of progestogens induced no unfavourable changes on haemostasis. In contrast, the use of ovulation inhibitors resulted in an acceleration of coagulation and fibrinolysis. This is primarily induced by the marked action of ethinylestradiol on hepatic and vascular function. Progestogens with androgenic properties may counteract the estrogen-induced changes in the hepatic synthesis of platelet aggregation and readiness for coagulation. Estrogen and progesterone receptors are localized in endothelial and smooth muscle cells of the vessel wall, but there are differences in the response of veins and arteries to sex steroids. Estrogens and progestogens may influence collagen and elastin synthesis, and the release of vasoactive compounds and of factors controlling fibrinolysis from endothelium. In veins, progestogens may increase distensibility and capacitance resulting in a decreased blood flow. In predisposed women, this may lead to venous stasis and thrombosis. In arteries, progestogens may act as vasoconstrictors, and may enhance vasospasms at sites of injured endothelium which finally may lead to ischemic diseases.

Mechanisms of estrogen-induced vasodilation: in vivo studies in canine coronary conductance and resistance arteries

OBJECTIVES

We sought to examine the immediate vasodilator effect of intracoronary estrogen on epicardial and resistance coronary arteries in 19 dogs.

BACKGROUND

Although estrogen reportedly dilates coronary arteries in vitro, the site and mechanisms of its action have not been fully defined in vivo.

METHODS

Epicardial coronary artery dimensions and coronary flow velocity were assessed using simultaneous intracoronary two-dimensional and Doppler ultrasound.

RESULTS

Estrogen (0.1 and 1 mumol/liter) induced a significant increase in coronary cross-sectional area, flow velocity and volumetric blood flow. Estrogen-induced vasodilation was not influenced either by pretreatment with N omega-nitro-L-arginine methyl ester (L-NAME) (100 mumol/liter intracoronary), indomethacin (5 mg/kg body weight intravenously), propranolol (0.75 mg/kg intravenously) or the classic estrogen receptor antagonist ICI 182,780 (10 mumol/liter). Balloon denudation of the endothelium did not attenuate estrogen-induced epicardial vasodilation. Pretreatment with glibenclamide (10 mumol/liter) attenuated estrogen-induced vasodilation only in epicardial arteries, as did verapamil (0.1 mumol/liter). Estrogen had no effect on a phenylephrine dose-response curve in either epicardial coronary arteries or the microcirculation.

CONCLUSIONS

Acute estrogen-induced dilation in canine coronary arteries is endothelium independent and is not mediated by the classic intracellular estrogen receptor but through non-genomic mechanisms, presumably at the membrane level, which in epicardial arteries may include effects on adenosine triphosphate-sensitive potassium or calcium channels, or both.

Ovarian senescence and its significance on uterine and ovarian perfusion

OBJECTIVE

To measure the flow velocity of the ovarian, uterine, radial, and spiral arteries in different age groups.

DESIGN

Serial measurements throughout the menstrual cycle in normal cycling women with documented fertility were compared with those in postmenopausal patients with and without hormone replacement therapy (HRT).

SETTING

Department of Obstetrics and Gynecology, University of Zagreb, Sveti Duh Hospital, Zagreb, Croatia.

PATIENTS

Two hundred fifty patients were analyzed: 120 healthy fertile women, 85 postmenopausal patients, and 45 postmenopausal patients receiving HRT.

INTERVENTIONS

All patients were examined by transvaginal color and pulsed Doppler.

MAIN OUTCOME MEASURE

Changes in the resistance index of flow velocity waveforms of the ovarian, uterine, radial, and spiral arteries.

RESULTS

Ovarian artery Doppler measurements in postmenopausal patients showed a significant difference when compared with the ovarian artery on the side containing dominant follicle or corpus luteum in healthy fertile group. Uterine and radial artery flow velocity analyses demonstrated significant positive correlations between the resistance index and years of menopause. In patients receiving HRT, a lowering effect occurred in the resistance index of the main uterine artery and its intramyometrial branches. Visualization of clear Doppler signals from the spiral arteries was possible in 30% of women who were menopausal for < 5 years. Increased vascular impedance was the typical finding in this vessel for this group of patients. The addition of HRT resulted in higher visualization rates of the spiral arteries and lowered resistance index values.

CONCLUSIONS

There are changes in the flow velocity patterns of the ovarian, uterine, radial, and spiral arteries with age. The fact that the uterine artery resistance index does not change significantly in the first postmenopausal years strongly supports the thesis that the aging process initially affects the uterus less than the ovary. Furthermore, the uterine environment can be manipulated more easily during the menopausal years by proper hormonal stimulation.

Color-Doppler velocimetry of uterine arteries in pregnant and nonpregnant patients during multiovulation induction for IVF

OBJECTIVES

To evaluate uterine artery resistance during multiovulation induction in relation to the implantation rate in patients attending in vitro fertilization (IVF) cycles.

PATIENTS

Multiovulation induction for IVF was monitored by daily determination of the pulsatility index (PI) of the uterine arteries, obtained by a transvaginal probe (6.5 MHz) implemented with color-flow imaging. Doppler data were obtained from 5 days before hCG administration to the day of follicular aspiration. One IVF cycle was monitored in 70 patients. In 17 patients, 41 IVF cycles were monitored until a successful attempt occurred.

RESULTS

In the 70 patients studied during one IVF attempt, the PI of the uterine arteries significantly varied (P < 0.001) in the different phases of the cycle. In the 24 patients who conceived, a significantly lower PI (P < 0.03) was found throughout the cycle. This result was mainly due to a highly significant difference of PI values observed the day after hCG administration (P < 0.005). In the 17 patients who conceived after 1 to 4 negative in vitro fertilizations, no significant difference in PI was observed in the uterine artery resistance in cycles in which implantation was or was not successful.

CONCLUSIONS

Uterine artery resistance varies significantly during phases of the induction therapy. Uterine artery resistance is lower throughout the course of multiovulation induction in patients with higher pregnancy rates. The PI on the day after hCG administration was the best index of pregnancy rate. Low uterine artery resistance was present even in negative attempts in patients who eventually achieved a successful implantation. PI values < or = 3 can be considered a favorable prognostic factor for future IVF cycles.

Brain Stem Auditory Evoked Potentials: Effects of Ovarian Steroids Correlated with Increased Incidence of Bell's Palsy in Pregnancy

To investigate the effect of ovarian steroids on the brain stem during changes of estrogen and progesterone blood levels, we recorded brain stem auditory evoked potentials with increased stimulus rates from 26 women treated for sterility by menotropins (Pergonal and Metrodin). These women were divided into three groups according to their estrogen and progesterone blood levels. The brain stem auditory evoked potential results revealed a significant delay of peak III only, with an increased stimulus rate in the group with the highest estrogen level. Estrogen may cause a brain stem synaptic impairment, presumably because of ischemic changes, and thus also may be responsible for a higher incidence of Bell's palsy during pregnancy.

The role of color Doppler imaging in the diagnosis of polycystic ovary syndrome

OBJECTIVE

Our purpose was to evaluate whether intraovarian and uterine blood flow variations are associated with clinical, ultrasonographic, and endocrine polycystic ovary syndrome findings.

STUDY DESIGN

Thirty-two hirsute, oligomenorrheic patients and 18 volunteer women underwent in the early follicular phase ultrasonographic evaluation of ovarian volume, echodensity, and follicle number; transvaginal color Doppler measurement of the uterine and intraovarian vessel variations; and radioimmunologic dosage of luteinizing hormone, follicle-stimulating hormone, estradiol, progesterone, testosterone, androstenedione, and other hormonal compartments.

RESULTS

In the patients with polycystic ovary syndrome (increased luteinizing hormone/follicle-stimulating hormone ratio, elevated androstenedione levels, high number of subcapsular follicles by ultrasonography-augmented ovarian volume and echodensity) (n = 22) we observed, at Doppler analysis, significantly elevated uterine artery pulsatility index values associated with a typical low resistance index of stromal ovary vascularization. The pulsatility index was positively correlated with the luteinizing hormone/follicle-stimulating hormone ratio, and the resistance index was negatively correlated. The elevated uterine artery resistance was correlated with androstenedione levels.

CONCLUSION

Doppler analysis can be a valuable additional tool for the diagnosis of polycystic ovary syndrome.

Gastric microcirculatory changes of portal-hypertensive rats can be attenuated by long-term estrogen-progestagen treatment

It has been suggested that estrogen-progestagen therapy may be useful in preventing bleeding from gastric angiodysplasia, a vascular lesion similar to that described in portal-hypertensive gastropathy. In this study we assessed the effects of estrogen-progestagen therapy on gastric microcirculation and systemic and splanchnic hemodynamics in portal-hypertensive and sham-operated rats. One week after the surgical procedure (partial portal vein ligation or sham surgery), animals were given an intramuscular injection of a slow-release preparation of estrogen-progestagen or its vehicle. Two weeks later, gastric mucosal blood flow was measured by means of hydrogen gas clearance, a morphometrical analysis of gastric mucosal blood vessels was performed and systemic and splanchnic hemodynamics were evaluated with a radiolabeled-microspheres technique. In portal-hypertensive rats, estrogen-progestagen therapy induced a significant reduction in gastric mucosal blood flow, number of blood vessels and relative area of vessels. Similar changes, although of lesser magnitude, were achieved with estrogen or progestagen given separately and with the low dose of combined estrogen-progestagen. Estrogen-progestagen treatment also induced significant reductions in portal pressure and porto-collateral resistance without changing systemic or splanchnic hemodynamics. In contrast, estrogen-progestagen treatment did not induce changes in any of the parameters studied in sham-operated rats. We conclude that long-term estrogen-progestagen therapy reduces the gastric hyperemia, increased mucosal vessel density and portal pressure in portal-hypertensive rats.

Endovaginal Doppler flow measurements of the ovarian artery in patients with a normal menstrual cycle and with polycystic ovary syndrome during in vitro fertilization

Women with a normal menstrual cycle (n = 21, controls), polycystic ovary syndrome (n = 10) and hypogonadotropic amenorrhea (n = 3) were stimulated with clomiphen-citrate (4th day to 8th day of the cycle) and with human menopausal gonadotropin (8th day to 11th day). The vascular impedance of the ovary carrying the dominant follicles was monitored by endovaginal pulsed Doppler flow measurement. Simultaneously, serum levels of LH, E2 and 17-OHP were assayed. Contrary to controls, women with polycystic ovary syndrome or hypogonadotropic amenorrhea showed decreased hormone levels and no lowering of the vascular impedance. In controls, the lower pulsatility index is caused by neovascularization around the dominant follicle and by E2-induced vasodilatation in the ovarian artery.

Progesterone induces endothelium-independent relaxation of rabbit coronary artery in vitro

The effect of progesterone on isolated rabbit coronary arteries and its possible mechanism was investigated by measuring changes of isometric tension. Progesterone (1, 3, 10 and 30 microM) induced significant coronary relaxation in K+ (30 mM)-, prostaglandin F2 alpha (3 microM)- or Bay K 8644 (1 microM plus 15 mM K+)- precontracted arteries. There was no difference between endothelium-intact and -denuded coronary arteries from both male and female rabbits, precontracted with these three agents. Haemoglobin, indomethacin, methylene blue, glibenclamide or barium chloride did not affect the relaxation. In endothelium-denuded rabbit coronary arteries, progesterone shifted calcium concentration-dependent constrictor-response curves to the right, the maximal contraction was also reduced. The -log ED50s were 3.6 in control, and 3.3 and 2.9 after incubation with progesterone (3 and 30 microM), respectively. Similar results were obtained in rat aorta. We conclude that progesterone induces significant endothelium-independent relaxation in rabbit coronary arteries in vitro, possibly by affecting calcium influx.

Endothelium-independent relaxation of rabbit coronary artery by 17 beta-oestradiol in vitro

1. We assessed the relaxant effect of 17 beta-oestradiol (10(-7), 10(-6) and 10(-5) M) on rabbit isolated coronary arteries precontracted with prostaglandin F2 alpha (3 x 10(-6) M), high extracellular potassium (30 mM) and Bay K 8644 (10(-6) M) plus high extracellular potassium (15 mM) by measuring isometric tension. 17 beta-Oestradiol (10(-6) and 10(-5) M) induced significant relaxation in coronary arteries from male and female rabbits. No differences were seen between arteries with or without endothelium. There were also no differences between coronary arteries isolated from male and female rabbits. 2. Inhibitors of endothelium-derived relaxing factor and vasodilator prostanoids, namely, reduced haemoglobin, N omega-nitro-L-arginine methyl ester and indomethacin, did not affect the relaxation induced by 17 beta-oestradiol in endothelium-intact coronary arteries. 3. Methylene blue, an inhibitor of guanylate cyclase, did not affect the coronary artery relaxation induced by 17 beta-oestradiol. 4. The calcium concentration-dependent contraction curve in potassium-depolarization medium was shifted to the right by 17 beta-oestradiol (10(-6) and 10(-5) M) in the rabbit coronary artery and rat aorta. The -log EC50s of calcium in control and after incubation with 17 beta-oestradiol (10(-6) and 10(-5) M) were 3.7 +/- 0.09, 3.1 +/- 0.10 and 2.8 +/- 0.08 respectively in rabbit coronary arteries and 3.8 +/- 0.11, 3.3 +/- 0.14 and 2.9 +/- 0.15 in rat aorta. 5. The results indicate that 17 beta-oestradiol induces rabbit coronary artery relaxation by an endothelium-independent mechanism in vitro. A calcium antagonistic property may be involved in the mechanism of rabbit coronary arterial relaxation by 17beta-oestradiol.

Alpha 1-adrenergic receptors in pulmonary and systemic vascular smooth muscle. Alterations with development and pregnancy

alpha 1-Adrenergic receptors mediate vasoconstriction in the pulmonary and systemic vasculature. In sheep the in vivo vasoconstrictor response to alpha 1-adrenergic stimulation is less in the pulmonary circulation compared with the systemic circulation of the fetus, the response increases in both vascular beds with fetal and postnatal development, and it decreases in the systemic vasculature with pregnancy. In an effort to determine the mechanisms underlying these differences, alpha 1-adrenergic receptor binding characteristics were determined by using [3H]prazosin in intrapulmonary and systemic (thoracic aorta) vascular smooth muscle (VSM) from late-gestation fetal lambs and from pregnant and nonpregnant ewes. alpha 1-Adrenergic receptor density was less in fetal intrapulmonary VSM that in fetal aortic VSM (12.4 +/- 1.5 versus 29.4 +/- 3.2 fmol/mg protein, p less than 0.05), and it was less (p less than 0.05) in the fetus compared with the pregnant ewe in both intrapulmonary and aortic VSM (51.0 +/- 5.2 and 76.5 +/- 5.9 fmol/mg protein, respectively). alpha 1-Adrenergic receptor density in intrapulmonary VSM was similar in the pregnant and nonpregnant ewe (61.9 +/- 7.2 fmol/mg protein), whereas in aortic VSM it was less (p less than 0.05) in pregnant ewes compared with nonpregnant ewes (101.0 +/- 5.5 fmol/mg protein). alpha 1-Adrenergic receptor affinity was similar in all the VSM sources tested.(ABSTRACT TRUNCATED AT 250 WORDS)

Lymphocyte beta 2-adrenoceptor density during menstrual cycle and pregnancy, in delivery and puerperium

Lymphocyte beta 2-adrenoceptor density was determined in 11 women during the normal menstrual cycle and 15 women during normal pregnancy. No significant difference in lymphocyte beta 2-adrenoceptor density was established in this follow-up study during the menstrual cycle or pregnancy. Lower lymphocyte beta 2-adrenoceptor density was established just after delivery and in puerperium compared with that during pregnancy. It is likely that the high catecholamine concentration during parturition together with the duration of labour and delivery caused down-regulation of the beta 2-adrenoceptors. In puerperium the irregular day-rhythm and the stress of caring for the newborn may also have an effect.

Fetal male masculinization in control and prenatally stressed rats

The present experiments were designed to test the hypothesis that males in utero masculinize the development of other males. This effect was examined during fetal development in males from control and prenatally stressed rats. A code identified the number of cervical-flanking males between the target male and the cervical end of the uterus. The male parameters morphology (anogenital distance) and body, adrenal, and testis weights were recorded on the eighteenth and twentieth gestational days and categorized by the cervical-flanking male classification. At Day 18, control fetuses with two cervical-flanking males in utero displayed significantly greater anogenital distance values than did males with no cervical-flanking male. At Day 20, control fetuses with two cervical-flanking males had testicular weights significantly greater than those of fetuses with one or zero cervical positioned male. Prenatal stress markedly impaired male fetal development at gestational Days 18 and 20 while suppressing the cervical-flanking male effect. These results confirm and extend previous data that indicate: (a) prenatal stress disrupts normal fetal development, resulting in long-term changes; and (b) androgens via a cervical-flanking blood-flow mechanism influence littermate morphology and sexual development during the prenatal period. Our findings also demonstrate that a general masculinizing effect could not be made across the measured male parameters since the effect of males positioned at the cervical-flanking region in utero appears to be dependent upon maternal sources of variance. Finally, androgens prenatally have an apparent positive interaction with somatic growth.

Transvaginal pulsed Doppler measurement of blood flow velocity in the ovarian arteries during cycle stimulation and after follicle puncture

In experimental studies, an increase of the ovarian blood flow was found during cycle stimulation. In this study, the authors performed transvaginal pulsed Doppler measurements of the ovarian arteries in stimulated cycles before and after follicle puncture. Four days before follicle puncture, high flow velocities in systolis were found compared with diastolis. Toward the day of embryo transfer, a marked increase of the diastolic blood flow velocity was observed. In patients with high endocrine response, the pulsatility index (PI) was significantly lower compared with that of patients with low endocrine response. The technique of transvaginal pulsed Doppler measurements offers the possibility to study the alterations of the ovarian blood flow under physiologic and pathophysiologic conditions.

Effect of pregnancy and sex steroids on alpha 1-adrenoceptor mechanisms in the guinea-pig uterine vascular bed

Adrenoceptor mechanisms in the extrinsic uterine arteries from late pregnant guinea-pigs were characterized pharmacologically and compared with contractile responses of uterine arteries from non-pregnant and oophorectomized control, progesterone and oestrogen treated animals. Pregnancy caused an increase in diameter of the arteries, more pronounced the more distal they were. There was no change in potassium-evoked maximum contractions during pregnancy. Noradrenaline (10 nM to 1 mM), in the presence of cocaine (1 microM) and propranolol (0.1 microM), induced concentration-dependent contractions of the arterial segments, with approximately similar pD2 values. The maximum responses (Emax) were significantly increased during pregnancy and hormone supplementation. Prazosin (10 nM to 1 microM), but not rauwolscine (10 nM to 1 microM), antagonized noradrenaline-evoked contractions of the arteries. Isoprenaline (10 nM to 1 microM), in the presence of prazosin (0.1 microM) and cocaine (1 microM), had no relaxant effect on arteries contracted submaximally by prostaglandin F2a (5 microM). Neither cocaine nor normetanephrine modified noradrenaline-evoked contractions of the uterine artery. The results indicate that guinea-pig uterine vasoconstriction is mediated by alpha 1-adrenoceptors while relaxant beta-adrenoceptor effects, neuronal and extraneuronal uptake mechanisms are of minor importance. The observed increase in Emax may be due either to an increase in the number of alpha 1-adrenoceptors or to an enhanced pharmaco-mechanical coupling, which conceivably is regulated by sex steroids since this response was reproduced in castrated animals by hormone supplementation.

Hormonal influence on utero-ovarian blood flow distribution in the mid-luteal pseudopregnant rat

Uterine and ovarian blood flows and ovarian fractional perfusion were measured in adult rats anaesthetized with sodium pentobarbital i.p. on day 6 of pseudopregnancy, by using radioactive microspheres. Fifty i.u. human chorionic gonadotropin (hCG) was found to increase the fractional perfusion of the ovary, and this was at least partially accomplished at the expense of the uterine blood flow, since this was reduced. Noradrenaline (NA) infusion (2 nmol min-1) reduced ovarian as well as uterine blood flow acutely. After 20 min of NA infusion (2 nmol min-1), however, ovarian blood flow and fractional perfusion were increased, while no significant effect was seen for uterine blood flow. Antidiuretic hormone (ADH) in a 20-min infusion (1 nmol min-1) markedly reduced ovarian and uterine blood flows.

Catecholaminergic regulation of ovarian function in mammals: current concepts

A review of the rapidly accumulating data in the literature continues to support the notion that catecholamines regulate ovarian function, and extends the complexity of catecholaminergic effects on the ovary via interactions with pituitary and adrenal hormones. It is clear that catecholamines affect growth and differentiation of ovarian follicles, but their role in follicular rupture during ovulation and in corpus luteum function remains unclear. The effects of catecholamines (mediated by membrane receptors) on ovarian function probably should be considered paracrine but classic endocrine regulation of ovarian function cannot be ruled out. Myogenic tonus of ovarian vasculature appears to be regulated by catecholamines, and estrogens may enhance adrenergic receptors in ovarian smooth muscle cells.

Systemic and uterine responses to alpha-adrenergic stimulation in pregnant and nonpregnant ewes

Attenuated systemic pressor responses to infused angiotensin II characterize normal human and ovine pregnancy; moreover, uterine vascular refractoriness is greater than that of the systemic vasculature overall. It remains unclear whether this generalized refractoriness also pertains to other vasoconstrictors; therefore we studied simultaneous systemic and uterine responses to alpha-agonists in pregnant (n = 6) and nonpregnant (n = 6) sheep. Mean arterial pressure, heart rate, uterine blood flow, and cardiac output were measured before and during infusions of norepinephrine (0.456 to 45.84 micrograms/min) and phenylephrine (1.29 to 129 micrograms/min). Both alpha-agonists caused dose-dependent increases (p less than 0.01) in mean arterial pressure and systemic vascular resistance and decreases in cardiac output (p less than 0.01) in nonpregnant and pregnant animals; however, nonpregnant pressor responses exceeded pregnant ones. Nonpregnant ewes also had greater decreases in uterine blood flow (p less than 0.05) and increases in uterine vascular resistance (p less than 0.05); furthermore, increases in uterine vascular resistance exceeded those of systemic vascular resistance in both groups (p less than 0.01). Attenuated uterine and systemic responses to alpha-agonists characterize normal ovine pregnancy; however, in contrast to the results with angiotensin II, the uterine vascular bed is substantially more responsive to alpha-agonists than the systemic vasculature overall.