Expression of Luteinizing Hormone-Releasing Hormone (LHRH) and Type-I LHRH Receptor in Transitional Cell Carcinoma Type of Human Bladder Cancer.

Bladder cancer (BC) is the tenth most frequently detected cancer in both sexes. Type-I luteinizing hormone-releasing hormone (LHRH) receptor (LHRH-R-I) is expressed not only in the pituitary, but also in several types of cancer disease. There are few data about LHRH-R-I expression in human BC. This study aimed to investigate the expression of LHRH and LHRH-R-I in the transitional cell carcinoma (TCC) type of human BC. RNA was extracted from 24 human bladder tumor specimens and three BC cell lines. RT-PCR was performed to detect mRNA for LHRH and LHRH-R-I. The protein of LHRH-R-I was further studied by immunohistochemistry (IHC), ligand competition assay, and Western Blot. PCR products of LHRH were found in 19 of 24 (79%) specimens and mRNA of LHRH-R-I was detected in 20 of 24 specimens (83%). Positive immunostaining for LHRH-R-I with different expression intensity was found in all samples examined, showing negative correlation with TCC grade. Radioligand binding studies also showed the presence of specific LHRH-R-I and high affinity binding of LHRH analogs. The high incidence of LHRH-R in BC suggests that it could serve as a molecular target for therapy of human BC with cytotoxic LHRH analogs or modern powerful antagonistic analogs of LHRH.

New Metabolic Influencer on Oxytocin Release: The Ghrelin.

BACKGROUND: The hypothalamic⁻pituitary axis by secreting neuropeptides plays a key role in metabolic homeostasis. In light of the metabolic regulation, oxytocin is a potential neuropeptide for therapies against obesity and related disorders. The aim of our study is to measure ghrelin-induced oxytocin secretion in rats and to detect the changes after administration of ghrelin antagonist. METHODS: Ghrelin was administrated centrally (intracerebroventricular, i.c.v., 1.0, 10.0, and 100.0 pmol) or systemically (intravenous, i.v., 1.0, and 10.0 nmol). [d-Lys³]-GHRP-6 ghrelin antagonist was injected 15 min before ghrelin injection in a dose of 10.0 pmol i.c.v. and 10.0 nmol i.v. RESULTS: Either i.c.v. or i.v. administration of ghrelin dose-dependently increased the plasma oxytocin concentration. Following pretreatment with the ghrelin antagonist [d-Lys³]-GHRP-6, the high plasma oxytocin level induced by ghrelin was significantly reduced. CONCLUSION: The results indicate that the release of oxytocin is influenced directly by the ghrelin system. Examination of the mechanism of ghrelin-induced oxytocin secretion is a new horizon for potential therapeutic options.

Is there a role of inducible nitric oxide synthase activation in the delayed antiarrhythmic effect of sodium nitrite?

This study aimed to examine whether inducible nitric oxide synthase (iNOS) plays a role in the delayed antiarrhythmic effect of sodium nitrite. Twenty-one dogs were infused intravenously with sodium nitrite (0.2 µmol·kg-1·min-1) for 20 min, either in the absence (n = 12) or in the presence of the iNOS inhibitor S-(2-aminoethyl)-isothiourea (AEST) (total dose 2.0 mg·kg-1 i.v., n = 9). Control dogs (n = 12) were given saline. Twenty-four hours later, all of the dogs were subjected to a 25 min period occlusion of the left anterior descending coronary artery followed by rapid reperfusion. Dogs treated with AEST and nitrite received again AEST prior to the occlusion. Compared with the controls, sodium nitrite markedly reduced the number of ectopic beats, the number and incidence of ventricular tachycardia, and the incidence of ventricular fibrillation during occlusion and increased survival (0% versus 50%) from the combined ischaemia and reperfusion insult. Although AEST completely inhibited iNOS activity, the nitrite-induced increase in NO bioavailability during occlusion was not substantially modified. Furthermore, AEST attenuated but did not completely abolish the antiarrhythmic effect of nitrite. The marked delayed antiarrhythmic effect of sodium nitrite is not entirely due to the activation of iNOS; other mechanisms may certainly play a role.

GABAergic neurogliaform cells represent local sources of insulin in the cerebral cortex.

Concentrations of insulin in the brain are severalfold higher than blood plasma levels. Insulin in the brain regulates the metabolism, molecular composition, and cognitive performance of microcircuits and reduces food intake; cerebral insulin levels are altered in diabetes, aging, obesity, and Alzheimer's disease. Released by pancreatic ß cells, insulin passes the blood-brain barrier, but sources of locally released insulin still remain unclear. We find that insulin is strongly expressed in GABAergic neurogliaform cells in the cerebral cortex of the rat detected by single-cell digital PCR. Focal application of glucose or glibenclamide to neurogliaform cells mimics the excitation suppressing effect of external insulin on local microcircuits via insulin receptors. Thus, neurogliaform cells might link GABAergic and insulinergic action in cortical microcircuits.

Determination of 17α-hydroxylase-C17,20-lyase (P45017α) enzyme activities and their inhibition by selected steroidal picolyl and picolinylidene compounds.

17α-hydroxylase-C17,20-lyase (P45017α) is a key regulator enzyme of the steroid hormone biosynthesis in both the adrenals and the testes. Inhibition of this enzyme can block androgen synthesis in an early step, and may thereby be useful in the treatment of several androgen-dependent diseases. We developed radio-substrate in vitro incubation methods for the determination of the distinct 17α-hydroxylase and C17,20-lyase activities of the enzyme using rat testicular homogenate as enzyme source. With this method we have studied the inhibiting activity of selected steroidal picolyl and picolinylidene compounds. Tests revealed a substantial inhibitory action of the 17-picolinyliden-androst-4-en-3-one compound.

[In the labyrinth of calcium metabolism]. / A kalcium-anyagcsere útvesztoi.

The authors present the case of a 27-year-old male patient. In 2010, he suffered from a bone fracture of the pelvis. As imaging techniques showed multiple osseal lytic lesions, diagnostic investigations were performed for multiple myeloma. Later, a mass lesion measuring 37 mm in size was removed from the left side of his mandible. Histology revealed a giant-cell tumour of the bone and oncologic therapy was considered. However, before this planned treatment a PET-CT was performed, which showed numerous distinct lesions with enhanced glucose metabolism in the skeleton as well as in soft tissue behind the right lobe of the thyroid. Hence, the patient was referred to endocrinologists. On the basis of severe hypercalcemia (serum calcium 3.66 mmol/l) and high serum parathyroid hormone level (162.5 pmol/l) the diagnosis of a right sided parathyroid tumour was established. After surgical excision of the parathyroid tumour, high levels of serum calcium and parathyroid hormone returned to normal. Histology failed to show malignancy and the patient recovered soon. This case report may shed some light on the importance of serum calcium measurements and the differential diagnostic significance of primary hyperparathyroidism.

The osmotically and histamine-induced enhancement of the plasma vasopressin level is diminished by intracerebroventricularly administered orexin in rats.

The effects of the centrally administered neuropeptides orexin-A on water intake and vasopressin (VP) secretion were studied in male Wistar rats (180-250 g). Different doses (10, 30, and 90 µg/10 µl) of the orexins and the specific orexin receptor-1 (OX(1)) antagonist SB 408124 (30 µg/10 µl) were administered intracerebroventricularly (i.c.v.) under anaesthesia, and the water consumption was measured during 6 h. A plasma VP level elevation was induced by histamine (10 mg/kg) or 2.5% NaCl (10 ml/kg) administered intraperitoneally (i.p.). The plasma VP levels were measured by radioimmunoassay. Increased water consumption was observed after the administration of 30 µg/10 µl orexin-A. There were no changes in basal VP secretion after the administration of different doses of the orexins. A significant increase in plasma VP concentration was detected following histamine administration. After 2.5% NaCl administration, there was a moderate VP level enhancement. Intracerebroventricularly administered orexin-A (30 µg/10 µl) blocked the VP level increase induced by either histamine or 2.5% NaCl administration. The inhibitory effects were prevented by the specific OX(1) receptor antagonist. In conclusion, the orexins increased water consumption. After 30 µg/10 µl orexin-A administration, the polydipsia was more pronounced. The OX(1) receptor antagonist significantly decreased the polydipsia. Histamine or hyperosmotic VP release enhancement was blocked by previously administered orexin. This inhibition was not observed following OX(1) receptor antagonist administration. Our results suggest that the effects of the orexins on water consumption or blockade of the histamine and osmosis-induced VP level increase are mediated by the OX(1) receptor.

Energy homeostasis regulatory peptides in hibernating grizzly bears.

Grizzly bears (Ursus arctos horribilis) are inactive for up to 6 months during hibernation. They undergo profound seasonal changes in food intake, body mass, and energy expenditure. The circa-annual regulation of metabolism is poorly understood. In this study, we measured plasma ghrelin, leptin, obestatin, and neuropeptide-Y (NPY) levels, hormones known to be involved in the regulation of energy homeostasis, in ten grizzly bears. Blood samples were collected during the active summer period, early hibernation and late hibernation. Plasma levels of leptin, obestatin, and NPY did not change between the active and the hibernation periods. Plasma total ghrelin and desacyl-ghrelin concentrations significantly decreased during the inactive winter period compared to summer levels. The elevated ghrelin levels may help enhance body mass during pre-hibernation, while the low plasma ghrelin concentrations during hibernation season may contribute to the maintenance of hypophagia, low energy utilization and behavioral inactivity. Our results suggest that ghrelin plays a potential role in the regulation of metabolic changes and energy homeostasis during hibernation in grizzly bears.

Steroidal ferrocenes as potential enzyme inhibitors of the estrogen biosynthesis.

The potential inhibitory effect of diverse triazolyl-ferrocene steroids on key enzymes of the estrogen biosynthesis was investigated. Test compounds were synthesized via copper-catalyzed cycloaddition of steroidal azides and ferrocenyl-alkynes using our efficient methodology published previously. Inhibition of human aromatase, steroid sulfatase (STS) and 17ß-hydroxysteroid dehydrogenase type 1 (17ß-HSD1) activities was investigated with in vitro radiosubstrate incubations. Some of the test compounds were found to be potent inhibitors of the STS. A compound bearing ferrocenyl side chain on the C-2 displayed a reversible inhibition, whereas C-16 and C-17 derivatives displayed competitive irreversible binding mechanism toward the enzyme. 17α-Triazolyl-ferrocene derivatives of 17ß-estradiol exerted outstanding inhibitory effect and experiments demonstrated a key role of the ferrocenyl moiety in the enhanced binding affinity. Submicromolar IC50 and Ki parameters enroll these compounds to the group of the most effective STS inhibitors published so far. STS inhibitory potential of the steroidal ferrocenes may lead to the development of novel compounds able to suppress in situ biosynthesis of 17ß-estradiol in target tissues.

Calcitonin gene-related peptide levels in saliva of patients with burning mouth syndrome.

Burning mouth syndrome (BMS) is an intraoral burning sensation for which no medical or dental cause can be found. Recent studies suggest that primary neuropathic dysfunction might be involved in the pathogenesis of BMS. Calcitonin gene-related peptide (CGRP) plays an important role in the development of pain and serves as a biological marker of trigeminovascular activation. The aim of this study was to determine the levels of CGRP in the saliva of BMS patients and estimate the trigeminovascular activation in BMS. CGRP levels were measured, by RIA method in 78 BMS patients and 16 healthy subjects. The levels of CGRP were non-significantly decreased in BMS patients in comparison to healthy subjects. These results suggest that trigeminal nerve degeneration may be the underlying cause of BMS.

Enhanced In Vitro Antitumor Activity of GnRH-III-Daunorubicin Bioconjugates Influenced by Sequence Modification.

Receptors for gonadotropin releasing hormone (GnRH) are highly expressed in various human cancers including breast, ovarian, endometrial, prostate and colorectal cancer. Ligands like human GnRH-I or the sea lamprey analogue GnRH-III represent a promising approach for the development of efficient drug delivery systems for targeted tumor therapy. Here, we report on the synthesis and cytostatic effect of 14 oxime bond-linked daunorubicin GnRH-III conjugates containing a variety of unnatural amino acids within the peptide sequence. All compounds demonstrated a reduced cell viability in vitro on estrogen receptor α (ERα) positive and ERα negative cancer cells. The best candidate revealed an increased cancer cell growth inhibitory effect compared to our lead-compound GnRH-III-[4Lys(Bu),8Lys(Dau=Aoa)]. Flow cytometry and fluorescence microscopy studies showed that the cellular uptake of the novel conjugate is substantially improved leading to an accelerated delivery of the drug to its site of action. However, the release of the active drug-metabolite by lysosomal enzymes was not negatively affected by amino acid substitution, while the compound provided a high stability in human blood plasma. Receptor binding studies were carried out to ensure a high binding affinity of the new compound for the GnRH-receptor. It was demonstrated that GnRH-III-[²ΔHis,³d-Tic,4Lys(Bu),8Lys(Dau=Aoa)] is a highly potent and promising anticancer drug delivery system for targeted tumor therapy.

Pharmacokinetics and pharmacodynamics of levofloxacin in critically ill patients with ventilator-associated pneumonia.

The pharmacokinetics of levofloxacin and outcome of levofloxacin therapy in critically ill patients with ventilator-associated pneumonia (VAP) were assessed. Further theoretical considerations regarding the pharmacokinetic/pharmacodynamic (PK/PD) appropriateness of levofloxacin therapy were made. Twelve patients completed the study, all of whom were treated with a standard intravenous levofloxacin regimen (2x500 mg on Day 1, then 1x500 mg daily). The maximum free plasma levofloxacin concentration (fC(max,ss)) and the area under the free concentration-time curve (fAUC) were 8.13+/-1.64 mg/L and 49.63+/-15.60 mgh/L, respectively. Optimal PK/PD target parameters were achieved in 10 patients; clinical success was attained in 11 of the 12 patients who completed the study. Bacterial eradication was obtained in 9 of the 11 cases with microbiologically confirmed bacteriological aetiology. Intravenous levofloxacin therapy (500 mg/day) was proven to be an effective regimen in this limited number of patients with VAP. However, theoretical considerations based on PK/PD indices predict that, with the current susceptibility breakpoint of 2mg/L, even higher levofloxacin doses (e.g. 1000 mg) could result in treatment failures in infections caused by pathogens labelled as levofloxacin-susceptible in the microbiology report.

Elevated levels of circulating insulin-like growth factor-I, IGF-binding globulin-3 and testosterone predict hormone-dependent breast cancer in postmenopausal women: a case-control study.

There is increasing evidence that different types of breast cancers are related to distinct risk factors. We analyzed the risk of breast cancer with respect to circulating insulin-like growth factor (IGF)-I, IGF-binding protein (IGFBP)-3, 17beta-estradiol, estrone, testosterone, androstenedione and sex hormone-binding globulin (SHBG), taking into consideration the characteristics of the tumors. Plasma hormone levels of 102 postmenopausal patients with breast cancer detected by mammography screening, and 102 matched controls were analyzed in relation to the histological type, the status of the estrogen receptor (ER), the progesterone receptor (PR) and the HER2 in the tumors. Significant positive associations were revealed between the IGF-I concentration and the overall risk of breast cancer (OR=3.1, 95% CI: 1.5-6.2), ER+PR+ breast cancer (OR=2.4, 95% CI: 1.1-5.4) and ER+PR- breast cancer (OR=4.3, 95% CI: 1.2-14.3) when the highest and the lowest ranges of IGF-I were compared. Significant associations were also found between the highest and the lowest quartiles of testosterone, resulting in OR=4.1 (95% CI: 1.8-9.4) for the risks of breast cancer and OR=5.8 (96% CI: 2.1-16.2) of ER+PR+ breast cancer. A synergy was seen between IGF-I and testosterone levels. When both plasma IGF-I and testosterone were in the highest quartile ranges, an OR=26.4 (95% CI: 1.6-426.5, p=0.021) was computed for breast cancer overall. No significant synergistic effects could be demonstrated with other parameters. There were significant, 2.5-fold (95% CI: 1.2-5.6), and 16-fold (95% CI: 2.0-133.5) increases in the overall risks of breast cancer and of ER+PR- breast cancer, respectively, when the highest and the lowest quartiles of IGFBP-3 were compared. No associations were found between any of the hormones and the risk of ER-PR- tumors. The increased prevalence of ER+ breast cancers in patients with higher levels of IGF-I, IGFBP-3 or testosterone implicate these hormones in the etiology of hormone-dependent breast cancer. Additional analyses specific for breast cancer subtypes may shed light on the value of hormone determinations for tailored chemoprevention.

Sleep in spontaneous dwarf rats.

Spontaneous dwarf rats (SDRs) display growth hormone (GH) deficiency due to a mutation in the GH gene. This study investigated sleep in SDRs and their somatotropic axis and compared to Sprague-Dawley rats. SDRs had almost undetectable levels of plasma GH. Hypothalamic GH-releasing hormone (GHRH) mRNA was increased, whereas GHRH-receptor (GHRH-R) and somatostatin mRNAs were decreased in SDRs. Hypothalamic GHRH and somatostatin peptide content decreased in SDRs. Quantitative immunohistochemistry for GHRH and GHRH-R corroborated and extended these findings. In the arcuate nucleus, the number of GHRH-positive cells was significantly higher, whereas GHRH-R-positive perikarya were diminished in SDRs. Cortical GHRH and GHRH-R measurements showed similar expression characteristics as those found in the hypothalamus. SDRs had less rapid eye movement sleep (REMS) and more non-REMS (NREMS) than the control rats during the light period. The electroencephalogram (EEG) delta and theta power decreased during NREMS in the SDRs. After 4-h of sleep deprivation, SDRs had a significantly reduced REMS rebound compared to the controls, whereas NREMS rebound was normal in SDRs. The enhancement in delta power was significantly less than in the control group during recovery sleep. Intracerebroventricular (icv) administration of GHRH promoted NREMS in both strains of rats; however, increased REMS and EEG delta activity was observed only in control rats. Icv injection of insulin-like growth factor 1 increased NREMS in control rats, but not in the SDRs. These results support the ideas that GHRH is involved in NREMS regulation and that GH is involved in the regulation of REMS and in EEG slow wave activity regulation during NREMS.

Microwave assisted synthesis and biomedical potency of salicyloyloxy and 2-methoxybenzoyloxy androstane and stigmastane derivatives.

A convenient microwave assisted solvent free synthesis as well as conventional synthesis of salicyloyloxy and 2-methoxybenzoyloxy androstane and stigmastane derivatives 7-19 from appropriate steroidal precursors 1-6 and methyl salicylate is reported. The microwave assisted synthesis in most cases was more successful regarding reaction time and product yields. It was more environmentally friendly too, compared to the conventional method. The antioxidant activity and cytotoxicity of the synthesized derivatives were evaluated in a series of in vitro tests, as well as their inhibition potency exerted on hydroxysteroid dehydrogenase enzymes (Δ(5)-3ßHSD, 17ßHSD2 and 17ßHSD3). All of the tested compounds were effective in OH radical neutralization, particularly compounds 9, 11 and 14, which exhibited about 100-fold stronger activity than commercial antioxidants BHT and BHA. In DPPH radical scavenging new compounds were effective, but less than reference compounds. 2-Methoxybenzoyl ester 10 exhibited strong cytotoxicity against MDA-MB-231 cells. Most compounds inhibited growth of PC-3 cells, where salicyloyloxy stigmastane derivative 15 showed the best inhibition potency. Compounds 9, 10 and 11 were the best inhibitors of 17ßHSD2 enzyme. X-ray structure analysis and molecular mechanics calculations (MMC) were performed for the best cytotoxic agents, compounds 10 and 15. A comparison of crystal and MMC structures of compounds 10 and 15 revealed that their molecules conformations are stable even after releasing of the influence of crystalline field and that the influence of crystal packing on molecular conformation is not predominant.

Sleep. A physiologic role for IL-1 beta and TNF-alpha.

Interleukin-1 beta (IL-1 beta) and tumor necrosis factor-alpha (TNF-alpha) are involved in physiologic sleep regulation. Administration of exogenous IL-1 beta or TNF-alpha induces increased non-rapid eye movement sleep (NREMS). Inhibition of IL-1 or TNF reduces spontaneous sleep. There is a diurnal rhythm of TNF-alpha mRNA and IL-1 beta mRNA in brain with highest levels occurring during peak sleep periods. Mice lacking either the TNF 55-kD receptor or the IL-1 type I receptor sleep less than do strain controls. IL-1 beta and TNF-alpha are part of a larger biochemical cascade involved in sleep regulation; other somnogenic substances in this cascade include growth hormone-releasing hormone and nitric oxide. Several additional substances are involved in inhibitory feedback mechanisms, some of which inhibit IL-1 and TNF. A major challenge to sleep research is to define how and where these molecular steps produce sleep.

Alterations in EEG activity and sleep after influenza viral infection in GHRH receptor-deficient mice.

Viral infections induce excess non-rapid eye movement sleep (NREMS) in mice. Growth hormone-releasing hormone receptor (GHRH receptor) was previously identified as a candidate gene responsible for NREMS responses to influenza challenge in mice. The dwarf lit/lit mouse with a nonfunctional GHRH receptor was used to assess the role of the GHRH receptor in viral-induced NREMS. After influenza A virus infection the duration and intensity [electroencephalogram (EEG) delta power] of NREMS increased in heterozygous mice with the normal phenotype, whereas NREMS and EEG delta power decreased in homozygous lit/lit mice. Lit/lit mice developed a pathological state with EEG slow waves and enhanced muscle tone. Other influenza-induced responses (decreases in rapid eye movement sleep, changes in the EEG high-frequency bands during the various stages of vigilance, hypothermia, and decreased motor activity) did not differ between the heterozygous and lit/lit mice. GH replacement failed to normalize the NREMS responses in the lit/lit mice after influenza inoculation. Decreases in NREMS paralleled hypothermia in the lit/lit mice. Lung virus levels were similar in the two mouse strains. Lit/lit mice had a higher death rate after influenza challenge than the heterozygotes. In conclusion, GHRH signaling is involved in the NREMS response to influenza infection.

Alterations in GHRH binding and GHRH receptor mRNA in the pituitary of adult dw/dw rats.

Lewis dwarf (dw/dw) rats exhibit growth hormone (GH) deficiency and growth retardation linked to a malfunction of GHRH signaling. In this study, GHRH-receptor (GHRH-R) binding and mRNA in the pituitary of adult male dw/dw and age-matched normal Lewis rats was measured by radioligand binding assay and real-time PCR. Only one of nine pools of dw/dw pituitary membranes revealed detectable binding of [His(1), 125I-Tyr(10), Nle(27)]hGHRH(1-32) amide (B(max); 4.3 fmol/mg protein). In contrast, GHRH-R binding was 22.4 +/- 2.60 fmol/mg protein in normal Lewis rats. mRNA for GHRH-R was detectable in all dw/dw rat pituitaries examined, averaging 21% that of Lewis rats. Low expression of GHRH-R reflects reduced GHRH-R mRNA as well as a possible reduction in translation of the receptor protein.

The effect of urocortin I on the hypothalamic ACTH secretagogues and its impact on the hypothalamic-pituitary-adrenal axis.

Urocortin I (UCN I) is a structural analogue of corticotropin-releasing factor (CRF), which, together with arginine-vasopressin (AVP), are the principle adrenocorticotropic hormone (ACTH) secretagogues in mammals. The aim of the present study was to investigate the effects of UCN I on the hypothalamic CRF and AVP concentration and its impact on the hypothalamic-pituitary-adrenal (HPA) axis. First, male Wistar rats were injected intracerebroventricularly (ICV) with 0.5, 1, 2 and 5 µg of UCN I. After 30 min hypothalamic CRF and AVP concentrations were determined by immunoassays. In parallel, the trunk blood was collected and plasma ACTH and corticosterone concentration was determined by ELISA and chemofluorescent assay, respectively. Second, rats were pretreated ICV with selective antagonists of receptors being implicated in the regulation of the HPA axis (0.1 µg antalarmin for CRFR1, 1 µg astressin 2B for CRFR2 or 0.1 µg deamino-Pen1,Tyr2,Arg8-vasopressin for AVPR3) and treated ICV with the most effective dose of UCN I (5 µg). After 30 min plasma corticosterone concentration was determined by chemofluorescent assay. UCN I induced dose-dependent augmentation of the hypothalamic CRF and AVP concentration, associated with dose-dependent elevation of the plasma ACTH and corticosterone concentration. The most significant effect of UCN I on the plasma corticosterone concentration was inhibited by antalarmin, but was not influenced by astressin 2B or deamino-Pen1,Tyr2,Arg8-vasopressin. The present study demonstrates that UCN I modulates the concentration of the hypothalamic ACTH secretagogues in parallel with the concentration of the plasma ACTH and corticosterone. Our results suggest that UCN I may activate the HPA axis by stimulation of the hypothalamic CRF production, and this process is mediated by CRFR1, and not by CRFR2. UCN I may stimulate the AVP production, as well, but, based on the results with AVPR3 antagonist, this effect is not involved in the regulation of the HPA axis.

The effect of acute simvastatin administration on the severity of arrhythmias resulting from ischaemia and reperfusion in the canine: Is there a role for nitric oxide?

The present study has examined the effects and the possible mechanisms of a single dose of simvastatin on the severity of arrhythmias resulting from a 25min occlusion and reperfusion of the left anterior descending coronary artery in anaesthetized (chloralose and urethane) dogs. The control animals (n=16) were given the solvent of simvastatin by slow (over 5min) intracoronary (ic.) injection just prior to the occlusion. Twenty-six dogs were treated with simvastatin (0.1mg/kg) by the same route, both in the absence (n=15) and in the presence (n=11) of l-NAME. This latter was administered (5mg/kg, ic.) either alone (n=12) or 10min before the simvastatin treatment. The severity of ischaemia (epicardial ST-segment, inhomogeneity) and ventricular arrhythmias (ventricular premature beats [VPBs], ventricular tachycardia [VT] and fibrillation [VF]), plasma nitrite/nitrate levels, myocardial superoxide production and eNOS activity were assessed. Compared with controls simvastatin significantly reduced the number of VPBs (289±34vs. 94±25) and the episodes of VT (5.6±1.3vs. 0.3±0.2), the incidence of VT (88% vs. 20%) and VF (56% vs. 0%) during occlusion and increased survival (0% vs. 33%) on reperfusion. There were also less marked ischaemic changes in the simvastatin-treated dogs than in the controls. Simvastatin preserved eNOS activity and nitric oxide (NO) bioavailability during occlusion and attenuated superoxide production following reperfusion. All these effects of simvastatin (except for the protection against VF) were reversed by l-NAME. We conclude that simvastatin given just prior to ischaemia/reperfusion reduces the severity of arrhythmias. This effect involves both NO-dependent and NO-independent mechanisms.