A Post-reflective Examination of the Physical and Mental Health Suffering During COVID-19 Through the Lens of Christ's Kenotic and Redemptive Act.

The COVID-19 global pandemic has brought unprecedented physical and mental health challenges to many, making the exploration of the spiritual dimension of suffering increasingly meaningful and relevant. Pope John Paul II's theologico-pastoral approach in Salvifici Doloris (SD) sheds light on how spiritual reflections and pastoral care anchored on the theology of Jesus Christ's sufferings can be put together to contribute to post-COVID-19 reflections. Given this context, this paper explores the perceptions and coping mechanisms of COVID-19 patients as they navigate the challenges of their illness. By examining patient experiences gleaned from medical and scientific journals, the study underscores the necessity of supporting individuals suffering from various diseases. As John Paul II thoughtfully remarks in Salvifici Doloris, there is a profound need to address patients' inquiries about "the cause, the reason, and equally, the purpose of suffering, and, in brief, a question about its meaning." Taking this into account, this paper contextualizes the theology of suffering articulated by Pope John Paul II in SD within the experiences of patients who contracted COVID-19 during the global pandemic. To embark on this discussion, the following themes about suffering are expounded: First, Insights into the Weight of Suffering Among Persons who Contracted COVID-19. Second, Understanding of Suffering in Salvifici Doloris, and Third, The Salvific Meaning of Suffering in COVID-19 and its Transformative Experience.

Endometrial response to concurrent treatment with vaginal progesterone and transdermal estradiol.

ABSTRACT Objective To describe the effect of the intermittent administration of vaginal progesterone and a low-dose estradiol patch on endometrial stability, as assessed by the rate of amenorrhea and endometrial stimulation. Methods This was an open study in which 64 moderately symptomatic, postmenopausal women were treated in the outpatient clinic of our University Hospital for different intervals up to 1 year. The treatment consisted of a combination of patches delivering 25 µg/day estradiol and intravaginal pills containing 100 mg of micronized progesterone. Patches and pills were administered concomitantly in a twice-a-week protocol. The endometrial response was assessed by endovaginal ultrasound completed with suction biopsy when required. Results Both cumulative amenorrhea and no-bleeding rates increased progressively and reached 88.9% and 100.0%, respectively, by the 12th month. Isolated or repetitive episodes of bleeding, bleeding and spotting, or only spotting were reported by three, four, and 12 women, respectively. Endometrial thickness remained unaltered. Endometrium was atrophic in the seven women in whom a biopsy was performed. Conclusion The substantially reduced progestogen load determined by this combination achieved an acceptable incidence of spotting or bleeding when associated with a low estrogenic dose. There was no apparent endometrial stimulation. Additional studies are required to confirm this observation.

Progestogens reduce thromboxane production by cultured human endothelial cells.

OBJECTIVES: Progestogens have been poorly studied concerning their roles in endothelial physiology. Prostanoids are vasoactive compounds, such as thromboxane A2, a potent vasoconstrictor, and prostacyclin, a vasodilator. We examined the effects of two progestogens used clinically, progesterone and medroxyprogesterone acetate, on thromboxane A2 production by cultured human umbilical vein endothelial cells (HUVEC) and investigated the role of progesterone receptors and the enzymes involved in production of thromboxane A2 and prostacyclin. METHODS: Cells were exposed to 1-100 nmol/l of either progesterone or medroxyprogesterone acetate, and thromboxane A2 production was measured in culture medium by enzyme immunoassay. Gene expression of prostacyclin synthase and thromboxane synthase was analyzed by quantitative real-time polymerase chain reaction. Expression of prostacyclin synthase protein was analyzed by Western blot. RESULTS: Both progestogens decreased thromboxane A2 release after 24 h. Protein and gene expression of prostacyclin synthase were increased after exposure to both progestogens, without changes in thromboxane synthase expression. These effects induced by progestogens were mediated through progesterone receptors, since they were decreased in the presence of the progesterone receptor antagonist RU486. The cyclo-oxygenase-1 selective inhibitor reduced thromboxane release. CONCLUSION: Progesterone and medroxyprogesterone acetate decreased HUVEC thromboxane release in a progesterone receptor-dependent manner, without changes in thromboxane synthase expression and enhanced prostacyclin synthase gene and protein expression.

Gene-gene interaction between CD40 and CD40L reduces bone mineral density and increases osteoporosis risk in women.

SUMMARY: We have analysed the association of single-nucleotide polymorphisms (SNPs) in CD40 and CD40L genes with bone mineral density (BMD) in our women. Results showed that women with TT genotype for rs1883832 (CD40) and for rs1126535 (CD40L) SNPs displayed reduced BMD and increased risk for osteopenia/osteoporosis. Our data notwithstanding, the results need to be replicated. INTRODUCTION: Recent data have revealed that the CD40/CD40L system can be implicated in bone metabolism regulation. Moreover, we previously demonstrated that rs1883832 in the CD40 gene was significantly associated with BMD and osteoporosis risk. The objective of the present work was to determine whether polymorphisms in CD40 and CD40L genes are associated with BMD and osteoporosis risk. METHODS: We conducted an association study of BMD values with SNPs in CD40 and CD40L genes in a population of 811 women of which 693 and 711 had femoral neck (FN) and lumbar spine (LS) densitometric studies, respectively. RESULTS: Women with the TT genotype for rs1883832 (CD40) showed a reduction in FN-BMD (P = 0.005) and LS-BMD (P = 0.020) when compared with women with the CC/CT genotype. Moreover, we found that rs1126535 (CD40L) was significantly associated with LS-BMD so that women with the TT genotype displayed lower BMD (P = 0.014) than did women with the CC/CT genotype. Interestingly, we have found a strong interaction between polymorphisms in these genes. Thus, women with the TT genotype for both rs1883832 and rs1126535 SNPs (TT + TT women) showed a lower age-adjusted BMD (Z-score) for FN (P = 0.0007) and LS (0.007) after adjusting by years since menopause, body mass index, smoking and menopausal status, densitometer type, hormone replacement therapy (HRT) use and HRT duration and after making the Bonferroni adjustment for multiple comparisons than did the remaining women. Logistic regression analysis adjusted by these covariates showed that TT + TT women had increased risk for FN (odds ratio (OR) = 2.76; P = 0.006) and LS (OR = 2.39; P = 0.020) osteopenia or osteoporosis than did the other women. CONCLUSIONS: Our results suggest that interaction between genetic variants in the CD40 and CD40L genes exerts a role on BMD regulation. Further studies, which we welcome, are needed to replicate these data in other populations.

Comparative effects of 17beta-estradiol, raloxifene and genistein on bone 3D microarchitecture and volumetric bone mineral density in the ovariectomized mice.

UNLABELLED: This study assessed the effect of estradiol, raloxifene and genistein on the preservation of bone 3D-microarchitecture and volumetric bone mineral density (vBMD) in the ovariectomized mouse model. Our results indicated that raloxifene was more effective in preserving bone ovariectomized-induced changes, the advantage being concentrated in both bone microarchitecture and vBMD. INTRODUCTION: This study assessed the effect of different estrogen receptor (ER) agonists on the preservation of bone 3D-microarchitecture and volumetric bone mineral density (vBMD) in the ovariectomized (OVX) mouse model. METHODS: Twelve-week-old female C57BL/6 mice were randomly assigned to one of five groups: (1) SHAM-operated + vehicle; (2) OVX + vehicle; (3) OVX + 17beta-estradiol (5 microg/kg); (4) OVX + raloxifene (1 mg/kg); (5) OVX + genistein (25 mg/kg), during 4-weeks. Bone microarchitecture and trabecular, cortical and total vBMD of distal femur were imaged by ex vivo microcomputed tomography (micro-CT). RESULTS: Ovariectomy produced a global deterioration involving both trabecular and cortical 3D-microarchitecture and vBMD. Raloxifene maintained both microarchitecture and vBMD, whereas estradiol prevented deterioration of some microstructural parameters, such as trabecular thickness (Tb.Th), trabecular bone pattern factor (Tb.Pf), and cortical periosteal perimeter (Ct.Pe.Pm), but did not completely block the loss in vBMD. Mice treated with genistein exhibited the less favourable profile in both vBMD and microstructural parameters preserving only cross-sectional bone area (B.Ar) and Ct.Pe.Pm in cortical bone. CONCLUSION: Our data indicate that, at the selected doses, raloxifene was more effective in preserving bone OVX-induced changes than either estradiol or genistein, the advantage being concentrated in both bone microarchitecture and vBMD.

A C >T polymorphism located at position -1 of the Kozak sequence of CD40 gene is associated with low bone mass in Spanish postmenopausal women.

UNLABELLED: This study evaluated the association of a polymorphism in the CD40 gene with BMD and risk of osteopenia or osteoporosis in a population of 602 postmenopausal women. Results showed that women with the TT genotype had lower BMD at femoral neck and spine sites and increased risk of osteopenia or osteoporosis. INTRODUCTION: Recent findings have demonstrated that the CD40/CD40L system, which is of main importance for the immune system, can also be implied in the regulation of bone metabolism. The main objective of the present work has been to clarify whether single nucleotide polymorphisms (SNPs) affecting genes of CD40/CD40L system could be linked with abnormalities in the level of bone mineral density (BMD) in menopausal women. METHODS: We performed an association study of BMD values with a SNP located at position -1 of the Kozak consensus sequence of CD40 gene (rs1883832; C>T) in a population of 602 postmenopausal women. RESULTS: Women with the TT genotype (8.6% of women) displayed a reduction in femoral neck BMD (FN BMD) and lumbar spine BMD (LS BMD) of 6.2% and of 6.3%, respectively, as compared to women with CC + CT genotype. Logistic regression analysis adjusted for age, weight, and height showed that women with the TT genotype had increased risk for FN (odds ratio: 2.34; 95% CI: 1.12-4.89) and LS (odds ratio: 2.49; 95% CI: 1.19-5.24) osteopenia or osteoporosis. CONCLUSIONS: Women with the TT genotype in rs1883832 SNP affecting to Kozak consensus sequence of CD40 gene had lower BMD at FN and at LS sites and increased risk of osteopenia or osteoporosis.

Selective estrogen receptor modulators and risk for coronary heart disease.

Coronary heart disease (CHD) is the leading cause of death in women in most countries. Atherosclerosis is the main biological process determining CHD. Clinical data support the notion that CHD is sensitive to estrogens, but debate exists concerning the effects of the hormone on atherosclerosis and its complications. Selective estrogen receptor modulators (SERMs) are compounds capable of binding the estrogen receptor to induce a functional profile distinct from estrogens. The possibility that SERMs may shift the estrogenic balance on cardiovascular risk towards a more beneficial profile has generated interest in recent years. There is considerable information on the effects of SERMs on distinct areas that are crucial in atherogenesis. The complexity derived from the diversity of variables affecting their mechanism of action plus the differences between compounds make it difficult to delineate one uniform trend for SERMs. The present picture, nonetheless, is one where SERMs seem less powerful than estrogens in atherosclerosis protection, but more gentle with advanced forms of the disease. The recent publication of the Raloxifene Use for The Heart (RUTH) study has confirmed a neutral effect for raloxifene. Prothrombotic states may favor occlusive thrombi at sites occupied by atheromatous plaques. Platelet activation has received attention as an important determinant of arterial thrombogenesis. Although still sparse, available evidence globally suggests neutral or beneficial effects for SERMs.

Estrogen receptor agonists and immune system in ovariectomized mice.

Several data implicate the immune system in bone lost after estrogen deficiency, however, some of the effects on the immune system of estrogen deficiency or of estrogen receptor (ER) modulation are not well established. In this study, the effect of ER agonists on the immune system in ovariectomized mice is analyzed. Mice were ovariectomized and were administered 17beta-estradiol (E2), raloxifene (RAL) or genistein (GEN). The effect of a 4-week treatment on bone turnover and on several parameters that reflect the status of the immune system was studied. Results show that ovariectomy provoked both uterine atrophy and thymic hypertrophy. Although RAL corrected thymic hypertrophy, only E2 corrected both. Ovariectomized mice showed increased levels of serum calcium and cathepsin K gene expression and decreased levels of serum alkaline phosphatase (ALP) activity, which suggests that there is a persistent alteration in bone metabolism. Moreover, ovariectomy increased B-cells and CD25+ cells, and decreased the percentages of T-cells and Cbfa1 gene expression in bone marrow (BM). All ER agonists corrected, although to different degrees, changes induced by the ovariectomy. Furthermore, results showed that it is essential to adjust ER agonist doses to avoid immunosuppression, since all ER agonists decreased BM T-cell levels.

Alterations in the phenotype and function of immune cells in ovariectomy-induced osteopenic mice.

BACKGROUND: Within the last few years, much evidence has been presented on the involvement of the immune system in certain types of bone loss, such as activated T cells in rheumatoid arthritis and in periodontitis. Estrogen deficiency induces bone loss; however, how this deficiency affects the immune system has not been sufficiently studied. METHODS: To evaluate the effects of estrogen withdrawal on the status and functionality of the immune system, mice were ovariectomized or sham-operated, and 5 weeks after surgery, when osteopenia had developed, several parameters were analysed in spleen and in bone marrow. We analysed bone turnover, cell phenotype by flow cytometry, cell function by cell proliferation assays, and the expression of several genes related to the process. RESULTS: Five weeks after ovariectomy, augmented osteoclastogenesis persisted in the bone marrow. In addition, the ovariectomized mice had more B-cells and CD3+ T-cells expressing the receptor activator of NF-kappaB ligand (CD3+/RANKL+). The ovariectomized mice had lower serum alkaline phosphatase activity, a normal amount of T cells, lower percentages of CD11b+ and CD51+ cells in the bone marrow, and a lower serum interferon-gamma level compared with sham-operated controls. CONCLUSIONS: The data suggest that, 5 weeks after ovariectomy, bone turnover remains imbalanced, with increased osteoclastogenesis and a decreased rate of bone formation. Moreover, there is an increase in B-cell formation, with normal and decreased percentages of T cells and myelomonocytic cells (CD11b+), respectively, in the bone marrow. Decreased serum interferon-gamma levels could be involved in the increased osteoclastogenesis found in the present work.

Cyclooxygenases regulation by estradiol on endothelium.

Estrogen and hormone replacement therapies are being tested to prevent the incidence of cardiovascular disease in postmenopausal women. In spite of the evidence from several epidemiological studies suggesting that estrogens protect against atherosclerosis and associated diseases, controversy exists. Moreover, it is important to develop synthetic compounds that achieve the beneficial effects of estrogens on the cardiovascular system while minimizing such undesirable effects on other tissues as the increased risk of endometrial and breast cancer. Some drugs that modulate estrogen function in a tissue-specific manner (Selective Estrogen Receptor Modulators; SERMs) have been discovered and are currently being used in clinical practice. An example of these is raloxifene. Clinical and experimental data support the consideration of endothelium as a target for estradiol and other sexual hormones. Among other actions, estradiol has been implicated in the control of prostacyclin production through cyclooxygenases (COX) regulation in endothelial cells. Prostacyclins are powerful vasodilators and potent inhibitors of platelet aggregation which are produced from free arachidonic acid through the catalytic activity of two COX: COX-1 and COX-2. Together, these COX represent the main control mechanism for prostacyclin production. Although several non-specific COX inhibitors have been available for decades (aspirin, indomethacin, ibuprofen), COX-2 selective inhibitors have been commercialized only within the last few years, thus making it possible to increase the study and treatment of different disorders. This review will discuss clinical and experimental data that document the endothelial effects of estradiol and SERMs on prostacyclin production and COX regulation, their vascular consequences, and their possible interactions with COX inhibitors.

Progestogens stimulate prostacyclin production by human endothelial cells.

BACKGROUND: The effects of progestogens on endothelial physiology are poorly studied. Prostacyclin is a potent vasodilator synthesized by two isoforms of cyclooxygenase (COX) in endothelium. We examined the effects of two clinically used progestogens, progesterone and medroxyprogesterone acetate (MPA), on prostacyclin production by cultured human umbilical vein endothelial cells (HUVEC) and the possible role of progesterone receptors and both COX enzymes. METHODS: Cells were exposed to 1-100 nmol/l of either progesterone or MPA and prostacyclin production was measured in culture medium. RESULTS: Both progestogens significantly increased prostacyclin release in a time- and dose-dependent manner, being higher than control after 24 h. Progesterone and MPA, both at 10 nmol/l, increased mRNA expression and protein content of both COX. All these effects were mediated through progesterone receptor activation, since they were abolished by treatment of cells with the progesterone receptor antagonist RU-486. Selective inhibitors of COX-1 and -2 (SC-560 and NS-398 respectively) reduced basal prostacyclin release, and eliminated increased production in response to progestogens. In combination with estradiol, progestogens had an additive effect without eliminating estradiol-induced prostacyclin production. CONCLUSIONS: Our results support the hypothesis that progesterone and MPA increased HUVEC prostacyclin production in a progesterone receptor-dependent manner, by enhancing COX-1 and COX-2 expression and activities.

Effect of delayed breeding on the reproductive performance of female mice.

The aim of the present study was to determine, in the mouse, whether maintaining females as virgins until an advanced reproductive age was associated with decreased reproductive performance and reproductive lifespan compared with females of the same age that were first mated with males at an earlier reproductive age. Randomly selected virgin hybrid (C57BL/6JIco female x CBA/JIco male) female mice were housed individually with a randomly selected 12- to 14-week-old hybrid male either at the age of 28 weeks (normal breeding group; n = 20) or 51 weeks (delayed breeding group; n = 23) for the rest of their reproductive life. Females were checked once daily to determine the day of parturition and to record the litter size and gender of pups at birth for each consecutive litter. At weaning, offspring were weighed and killed. Delayed breeding was associated with smaller litter sizes, both at birth and at weaning, a higher bodyweight of pups at weaning, a higher percentage of litters with at least one newborn pup cannibalised, earlier cessation of female reproductive life and a higher mortality rate of dams during the breeding period. These results show that delayed breeding in the mouse is associated with decreased reproductive performance and a shorter reproductive lifespan compared with females bred at an earlier reproductive age.

The effect of oral hormone replacement therapy on lipoprotein profile, resistance of LDL to oxidation and LDL particle size.

OBJECTIVES: To disclose if oral estradiol (E(2)), alone or in combination with natural progesterone (P) or medroxyprogesterone acetate (MPA), may modify the oxidizability of low density lipoprotein (LDL), and if the effect is achieved at physiological dosages. LDL oxidizability was assessed by the resistance to oxidation by copper and by the particle size profile, since small particles have increased oxidation susceptibility. METHODS: Thirty-three women received two consecutive, two-month length doses of 1 and 2 mg/day of oral E(2). They were then randomly assigned to a fourteen-day treatment of 2 mg/day E(2) plus either 300 mg/day P or 5 mg/day MPA. A parallel group of experiments was performed on a pool of baseline plasma, where hormones were added at the desired concentration. Lipoprotein levels, resistance of LDL to oxidation, and LDL particle diameter, were measured at baseline and after each treatment. RESULTS: Estradiol reduced LDL levels and increased high density lipoprotein (HDL) and triglycerides. P abolished these changes, whereas MPA only reversed the increase of HDL. Estradiol protected LDL from oxidation in a dose-dependent manner, although only at pharmacological concentrations (1 microM or higher). Both P and MPA were inert at either physiological or pharmacological concentrations. The size of the LDL particles remained unaffected except under MPA, in which it was reduced. CONCLUSIONS: Estradiol has a protective effect against LDL oxidation, although only at pharmacological dosages. P and MPA did not limit the E(2) action. The size of the LDL particles remained unaltered after each E(2) dose, but MPA, and not P, was associated with a diminution.

Metabolismo lipídico y aterogénesis femenina: acción de hormonas, serm y fitoestrógenos / Lipid metabolism and female atherogenesis. The action of hormones, SERMs and phytoestrogens

Objetivo: Revisar los efectos de la terapia hormonal sustitutiva, en sus distintas formas, en el metabolismo lipídico.Fuentes: Bibliografía médica hasta septiembre del año 2000 a través de MEDLINE.Conclusiones: Los estrógenos, combinados o no con progestágenos, inducen un perfil lipoproteico favorable. Buena parte de esa acción se ejerce a través de modificación en la cinética de partículas.Las acciones sobre oxidación de las lipoproteínas de baja densidad (LDL), o el tamaño de sus partículas, son motivo de polémica. Nuevos preparados, con capacidad de activar receptores estrogénicos, también demuestran ejercer acciones selectivas sobre el metabolismo lipídico. Objetivo: Revisar los efectos de la terapia hormonal sustitutiva, en sus distintas formas, en el metabolismo lipídico.Fuentes: Bibliografía médica hasta septiembre del año 2000 a través de MEDLINE.Conclusiones: Los estrógenos, combinados o no con progestágenos, inducen un perfil lipoproteico favorable. Buena parte de esa acción se ejerce a través de modificación en la cinética de partículas.Las acciones sobre oxidación de las lipoproteínas de baja densidad (LDL), o el tamaño de sus partículas, son motivo de polémica. Nuevos preparados, con capacidad de activar receptores estrogénicos, también demuestran ejercer acciones selectivas sobre el metabolismo lipídico (AU)

Impacto del metabolismo lipídico en la aterogénesis femenina / Impact of lipid metabolism in atherogenesis in women

Objetivo: Revisar los mecanismos que, ligados al metabolismo lipídico, determinan riesgo vascular en la mujer posmenopáusica.Fuentes: Bibliografía médica hasta septiembre del año 2000 a través de MEDLINE.Conclusiones: Nuevos datos, ligados a la modificación de partículas por oxidación o cambios en su tamaño, aclaran considerablemente la influencia de los lípidos en los procesos de aterogénesis (AU)

Modulation of the oestrogen receptor: a process with distinct susceptible steps.

The selective oestrogen receptor modulators (SERMs) constitute a group of substances which are capable of regulating the agonistic/antagonistic profile of the oestrogen receptor in distinct tissues. Their potential utility is considerable since, among the pleiotropic range of effects that oestrogens exert on their target tissues, they may provide a selective profile that better suits each clinical necessity. This review summarizes the principal steps of oestrogen action where modifications have resulted in changes of the effect profile. Three different steps of oestrogen action have been highlighted as being susceptible to modulation: type of ligand, particular species of oestrogen receptor, and particulars at the target tissue. Two main families of SERMs, the triphenylethylene derivatives, with tamoxifen as the main actor, and the benzothiophene derivatives, mainly represented by raloxifene, provide much of the basic and clinical knowledge on the influence of the type of ligand. Two types of oestrogen receptor, alpha and beta, add the second variable susceptible to modulating the response to receptor activation. Finally, the ligand-receptor complex may define particular events in its interaction with DNA, such as binding to promoters other than the oestrogen response element, recruitment of concrete sets of local transcription factors, or other options.

Pure anti-oestrogens.

Pure anti-oestrogens are a group of at least five new compounds which are able to antagonize the effects of oestrogen in all tissues and species studied. The mechanism by which the pure anti-oestrogens produce their effects remains in question, but all of them are competitive antagonists of the oestrogen receptors and, moreover, have been proposed to block the shuttling of oestrogen receptors into the cell nucleus. When studied in vitro, these compounds are able to block the oestrogen-stimulated growth of breast cancer cells. In animals, their ability to block the effects of oestrogen on breast, uterus, bone, cardiovascular system and other reproductive-associated tissues has been demonstrated. ICI 182780 has been used in preliminary clinical trials in women with advanced, tamoxifen-resistant breast cancer with promising results. Clinical trials with EM-800 are under way to assess the safety and tolerance and to obtain information on its efficacy in patients who have already been treated with tamoxifen. It seems reasonable to assume that pure anti-oestrogens will be a good alternative to tamoxifen in the treatment of breast cancer and also in some non-malignant gynaecological diseases.

The endometrial effects of SERMs.

The ideal selective oestrogen receptor modulator (SERM) would retain an oestrogen-like effect on the bones, the heart and cardiovascular apparatus, and the central nervous system, while acting as an anti-oestrogen on the breast and the genital tract. It seems, however, that such a compound is not available for clinical use yet. The uterine tissue, and particularly the endometrium, defines an area of special interest in the SERM action, since endometrial hyperplasia and cancer has been linked to agonistic oestrogen effects. Additionally, tamoxifen, the SERM which accumulates most of the clinical experience, has been associated with stimulatory effects on endometrium, including the development of cancer. In contrast, the more recent benzothiophenes, led by raloxifene, seem to operate as endometrial antagonists, thus providing an interesting alternative for clinical use. This review analyses the endometrial action of tamoxifen, including the information gathered from laboratory models, the observed endometrial effects in women using tamoxifen, and the epidemiological and molecular data which link the use of tamoxifen with endometrial cancer. A parallel examination of the raloxifene data presents the available experimental and clinical information, suggesting the endometrial neutrality of this compound.

Activation of N-methyl-D-aspartate receptors in rat brain in vivo following acute ammonia intoxication: characterization by in vivo brain microdialysis.

Ammonia is considered the main agent responsible for the neurological alterations in hepatic encephalopathy. It was suggested that ammonia toxicity is mediated by activation of N-methyl-D-aspartate (NMDA) receptors. The aim of this work was to assess, by in vivo brain microdialysis in freely moving rats, whether acute ammonia intoxication leads to activation of NMDA receptors in the cerebellum of the rat in vivo. We measured the effects of ammonia intoxication on the neuronal glutamate-nitric oxide-cyclic guanosine monophosphate (cGMP) pathway, by measuring the ammonia-induced increase of extracellular cGMP. Ammonia intoxication increases extracellular cGMP, and this increase is prevented by (5R,10S)-5-methyl-10,11-dihydro-5H-dibenzo[a, d]cyclohepten-5,10-imine hydrogen maleate (MK-801). There is a good correlation between the increase in cGMP and the seriousness of the neurological symptoms elicited by different doses of ammonia. Ammonia doses inducing coma did not affect extracellular glutamate, while doses leading to death increased it by 349%. The time courses of ammonia-induced increases in extracellular ammonia, cGMP, and glutamate indicate that NMDA receptor activation occurs before the increase in extracellular glutamate. Ammonia-induced increase in glutamate is prevented by MK-801. These results indicate that ammonia intoxication leads to activation of NMDA receptors in the animal in vivo, and that this activation is not caused by increased extracellular glutamate. The possible underlying mechanism is discussed.