Tail Artery Research Articles

Effect of phospholipase C inhibition on vascular smooth muscle contraction

Phospholipase C is the key enzyme responsible for the hydrolysis of membrane phospholipids phosphatidylinositol 4,5-bisphosphate (PIP 2 ) to two intracellular transmitters - diacylglycerol (DAG) and inositol triphosphate (IP 3 ). PLC activation of smooth muscle leads to an increase in the concentration of IP 3 and DAG which initiates the increase in the concentration of calcium ions into the cytoplasm as a result of the flow from the intracellular and then from extracellular pool. Main aim of this study was to evaluate the effect of PLC inhibitor U-73122 on vascular smooth muscle contraction stimulated pharmacologically with phenylephrine (PHE, α 1 -adrenoceptor agonist) and arg-vasopressin (AVP, vasopressin receptor agonist). Material and methods. Experiments were performed on isolated and perfused tail artery of Wistar rats. Contraction force in our model was measured by increased level of perfusion pressure with a constant flow. Results. Reactivity of vascular smooth muscle cells to PHE (10 -9 - 10 -3 M/L), and AVP (10 -10 – 10 -4 M/L), in the control group and in the presence of U-73122 – phospholipase C inhibitor at concentrations 1, 3 and 10 μM/l was analyzed. EC 50 values calculated for PHE and AVP were 7.52 (±0.97) x10 -8 M/L and 1.84 (±0.6) x10 -8 M/L, respectively. The concentration-response curves obtained for PHE and AVP in the presence of U-73122 were shifted to the rightward with a decrease in maximal responses. In the presence of U-73122 the significant and dose dependent reduction in perfusion pressure was found for both agonists for calcium influx from intracellular calcium stores and from extracellular space. Conclusion. Results of our experiments suggest that in the presence of phospholipase C inhibitors, contraction induced by G-protein coupled receptors activation may by effectively inhibited by reduction in calcium influx from intra and extracellular calcium stores.

Simvastatin reverses cardiomyocyte hypertrophy via the upregulation of phosphatase and tensin homolog expression.

The aim of the present study was to investigate the effects of simvastatin on the protein kinase B (PKB) signaling pathway and the expression of phosphatase and tensin homolog (PTEN). The effects of simvastatin were analyzed by administering the drug orally to male spontaneously hypertensive rats (SHRs) at a dose of 10 mg/kg/day, while the control animals received an equal volume of saline. The systolic pressure (mmHg) of the rat tail artery was measured prior to the initiation of the experiment, and once a week until the end of the experiment. At the end of the experiment, the animals were euthanized and the hearts were removed. The left ventricular and interventricular septum were weighed, after which the left ventricular mass/body mass ratio was calculated. In addition, cardiomyocytes isolated from Sprague Dawley rats were cultured with 15% fetal bovine serum to induce hypertrophy, following which the cells were treated with different doses of simvastatin. The in vitro effects were assessed by measuring the surface area of the cardiomyocytes, while the rate of protein synthesis was measured using a 3H-leucine incorporation assay and western blot analyses. Simvastatin was demonstrated to inhibit cardiomyocyte hypertrophy in the in vivo and in vitro experiments. Notably, simvastatin increased PTEN expression and inhibited PKB expression in the SHR model, as well as in the cardiomyocytes in culture. In addition, the use of PTEN antisense oligodeoxynucleotides was revealed to inhibit the effects of simvastatin on cardiomyocytes. Therefore, these results indicated that simvastatin was able to reverse cardiomyocyte hypertrophy in vivo and in vitro, possibly by increasing the expression of PTEN.

PP.34.40

Objective: To characterize the morphology of the brain vessels and glia in experimental modeling of hypertension in rats. Design and method: To create endothelial dysfunction in hypertensive model was reproduced NO deficit in rats in vivo. The animals of the experimental group on a daily basis with the drinking water was administered a NO-synthase blocker as methyl N-nitro-L-arginine (L-NAME, Sigma) for calculating the dose of 50 mg / kg / day. AH development was monitored by measuring the blood pressure of the tail artery at 8 weeks after the administration of L-NAME. (Group 1). The second group consisted of healthy rats that were in standard conditions (group 2). After euthanasia made histological preparations of rat brain, followed by light microscopy - Increase 20. Calculation of results was carried out using Image J. assessed such factors as distribution density of capillaries 1 mm2 (mm/mm), the specific density of the distribution of glial cells. Results: Distribution density of capillaries in the first group was - 32,64 ± 5,1 and 107,01 ± 7,2 in the second. In the first group, a significant decrease in the specific set of cell density neuroglia - 0,62 ± 0,03 as compared with the second group - 4,45 ± 0,05. In the rat model of hypertension microangiopathy showing signs of brain microvascular discharge cells and reduction in the number of neuroglia Conclusions: In the rat model of hypertension microangiopathy showing signs of brain microvascular discharge cells and reduction in the number of neuroglia

Antivibration Gloves: Effects on Vascular and Sensorineural Function, an Animal Model

Anti-vibration gloves have been used to block the transmission of vibration from powered hand tools to the user, and to protect users from the negative health consequences associated with exposure to vibration. However, there are conflicting reports as to the efficacy of gloves in protecting workers. The goal of this study was to use a characterized animal model of vibration-induced peripheral vascular and nerve injury to determine whether antivibration materials reduced or inhibited the effects of vibration on these physiological symptoms. Rats were exposed to 4 h of tail vibration at 125 Hz with an acceleration 49 m/s2. The platform was either bare or covered with antivibrating glove material. Rats were tested for tactile sensitivity to applied pressure before and after vibration exposure. One day following the exposure, ventral tail arteries were assessed for sensitivity to vasodilating and vasoconstricting factors and nerves were examined histologically for early indicators of edema and inflammation. Ventral tail artery responses to an α2C-adrenoreceptor agonist were enhanced in arteries from vibration-exposed rats compared to controls, regardless of whether antivibration materials were used or not. Rats exposed to vibration were also less sensitive to pressure after exposure. These findings are consistent with experimental findings in humans suggesting that antivibration gloves may not provide protection against the adverse health consequences of vibration exposure in all conditions. Additional studies need to be done examining newer antivibration materials.

Angiotensin II increases nerve-evoked contractions in mouse tail artery by a T-type Ca2+ channel-dependent mechanism

Angiotensin II (Ang II) increases sympathetic nerve-evoked contractions of arterial vessels. Here the mechanisms underlying this effect were investigated in mouse tail artery.Isometrically mounted segments of mouse distal tail artery were used to investigate the effects of endothelium denudation, blocking Ca2+ channels and inhibiting superoxide signalling on Ang II-induced facilitation of nerve-evoked contractions. In addition, in situ amperometry was used to assess effects of Ang II on noradrenaline release. Ang II (0.1–1nM) increased nerve-evoked contractions but did not change noradrenaline release. Losartan (Ang II type 1 receptor antagonist), but not PD 123319 (Ang II type 2 receptor antagonist), blocked the facilitatory effect of Ang II on nerve-evoked contractions. Ang II increased vascular muscle reactivity to phenylephrine and UK-14304 (α1- and α2-adrenoceptor agonists, respectively). Endothelial denudation increased nerve-evoked contractions and reduced the facilitatory effect of Ang II on these responses. Efonidipine (L- and T-type Ca2+ channel blocker) and NNC 55-0396 (T-type Ca2+ channel blocker) also attenuated this effect of Ang II, while nifedipine (L-type Ca2+ channel blocker) did not. Blockers of superoxide generation/signalling did not change the facilitatory effect of Ang II on nerve-evoked contractions. The findings indicate that Ang II increases the contribution of T-type Ca2+ channels to neural activation of the vascular muscle. In addition, Ang II appears to reduce the inhibitory influence of the endothelium on nerve-evoked contractions.

Effects of Resveratrol on Contractions of the Rat Tail Artery

In 2000, Naderali et. al. reported in Clinical Science (98:537-43) that resveratrol's direct vasorelaxant effect in vitro (on either adrenergic receptor-induced or high potassium-induced vascular smooth muscle contractions) was significantly greater in ring segments cut from mesenteric resistance arteries than from the main uterine conductance artery of female guinea pigs. Since then this important difference has not been confirmed in any other resistance versus conductance arterial tissues, and isolated from the same vasculature perfusing the same organ rather than different vessels perfusing different organs. The most distal and most proximal portions of the notably long ventral tail artery of the laboratory rat are commonly known for their unique structural and functional similarities to other resistance and conductance arteries (respectively) found throughout the rest of the body. Accordingly, we tested for relaxant effects of resveratrol in vitro in adrenergically pre-contracted rings cut from short segments of the distal and proximal portions of the tail artery from male rats. Its half-maximally effective concentration values were essentially identical (25±3 versus 27±3 micromolar) in distal versus proximal segments; results which do not confirm a greater relaxant effect of resveratrol in resistance versus conductance arterial tissues. Therefore, what Naderali et. al. previously observed may have been due to some other property that differed between their mesenteric and uterine arterial preparations. Support: MWU Master's Program.

Oroxylin A‐induced Endothelium‐dependent Constriction of Tail Arteries of Endotoxemic Hypotensive Rats

Refractory hypotension and vascular hyporeactivity in severe sepsis remain major clinical concerns. Here we report the induction of endothelium‐dependent constriction of tail arteries (TA) in endotoxemic hypotensive rats. In lipopolysaccharide (LPS)‐induced endotoxemic rats, oroxylin A (OroA, 15 mg/kg, iv) administered 6 hrs after LPS‐challenge promptly reversed diminished mean arterial pressure(MAP) and heart rate. OroA (1‐10 µM), which did not constrict isolated normal TA, repeatedly induced exclusive endothelium‐dependent, sustained constriction of isolated endotoxemic TA with intact‐endothelium (EC+). OroA‐induced constriction of was not blocked by endothelin‐1 (ET‐1) receptor antagonists (BQ123 or BQ788, 10 µM), but was blocked by inhibitors for RhoA/ROCK pathway. These results suggest that OroA‐induced endothelium‐dependent constriction of endotoxemic TA is mediated by non‐ET‐1‐substance(s) which activated muscle RhoA/ROCK pathway. OroA‐post‐treatment also suppressed, via inhibition of NF‐κB, inducible‐NOS expression and circulating NO. It is concluded that LPS upregulates endothelial non‐ET‐1‐vasoconstrictor(s) in endotoxemic TA. Its release by OroA activates muscle RhoA/ROCK pathway leading to prompt and sustained vasoconstriction that partly is caused by decreased circulating NO induced by OroA. The endothelium‐dependent constriction of TA and suppression of systemic inflammation as evidenced by OroA may offer a newstrategy for acute management of endotoxemic hypotensive shock (supported by MOST, TCU, and Tzu Chi Foundation).

Therapeutic Potential of S43126 to Treat Select Patients with Type 2 Diabetes and Hypertension

Novel therapeutic agents with reduced side‐effect profile are needed to treat type 2 diabetes. The objective of this study is to highlight the potential of a novel imidazoline compound S43126 as a future antidiabetic drug. We hypothesize that S43126 can exert beneficial effects in type 2 diabetes by a mechanism involving insulin release and insulin sensitization. Rat tail arteries were treated in a bath system with S43126 and other compounds to determine the contractile response to these agents. Control Zucker lean rats (ZLRs) and Zucker diabetic rats (ZDRs) were treated with S43126 or moxonidine for 2 weeks, and then plasma glucose and blood pressure were measured. Insulin release by mouse islets in response to varying doses of S43126 was determined. Western blot was used to determine the effect of S43126 on PKB phosphorylation. S43126 did not contract rat tail artery, but lowered blood glucose in ZDR by 31% relative to control, with no significant effect in ZLR. S43126 significantly reduce blood pressure in ZDR only. S43126 caused a dose‐dependent insulin release of up to 4 fold from mouse islet cells, only under conditions of high glucose. S43126 increased PKB phosphorylation which was blocked by efaroxan. These data suggests that S43126 decrease blood glucose by a mechanism involving insulin release, sensitization, or both. S43126 should be further studied as a possible agent to treat some patients who have type 2 diabetes and hypertension.

Synchronization in the Heart Rate and the Vasomotion in Rat Aorta: Effect of Arsenic Trioxide.

Arsenic trioxide (As2O3) is used clinically in the management of acute promyelocytic leukemia, and the use of electrocardiogram (ECG) in this management is important as arsenic use may cause distortion of the electrical properties with its attendant sequel. We studied the effect of As2O3 on vasomotion in rat aortic rings using isometric tension recordings and ECG in anesthetized rats. The results showed that As2O3 (10(-5) M) significantly (p < 0.01) reduced the frequency of acetylcholine (10(-5) M ACh)- and KCl (10 mM)-induced vasomotion, and it also increased the relaxation time (R t) of vasomotion. This effect was restored by 10(-8) M sodium nitroprusside (nitric oxide donor). ACh-induced NO release in the aorta was blunted in the presence of As2O3. The corrected QT interval (QTc) of the ECG, and time dilation (T d) of the pulse wave in the tail artery of the anesthetized rat were significantly (p < 0.05) increased in the arsenic-treated group (50 ppb As) versus control. In conclusion, data suggest that arsenic-induced reduction in vasomotion frequency of the isolated aortic rings is associated with a decreased bioavailability of NO, an increase in QTc and a decrease in the frequency of the pulse wave generated by the cardiac cycle in anesthetized rats.

Acute two-photon imaging of the neurovascular unit in the cortex of active mice.

In vivo two-photon scanning fluorescence imaging is a powerful technique to observe physiological processes from the millimeter to the micron scale in the intact animal. In neuroscience research, a common approach is to install an acute cranial window and head bar to explore neocortical function under anesthesia before inflammation peaks from the surgery. However, there are few detailed acute protocols for head-restrained and fully awake animal imaging of the neurovascular unit during activity. This is because acutely performed awake experiments are typically untenable when the animal is naïve to the imaging apparatus. Here we detail a method that achieves acute, deep-tissue two-photon imaging of neocortical astrocytes and microvasculature in behaving mice. A week prior to experimentation, implantation of the head bar alone allows mice to train for head-immobilization on an easy-to-learn air-supported ball treadmill. Following just two brief familiarization sessions to the treadmill on separate days, an acute cranial window can subsequently be installed for immediate imaging. We demonstrate how running and whisking data can be captured simultaneously with two-photon fluorescence signals with acceptable movement artifacts during active motion. We also show possible applications of this technique by (1) monitoring dynamic changes to microvascular diameter and red blood cells in response to vibrissa sensory stimulation, (2) examining responses of the cerebral microcirculation to the systemic delivery of pharmacological agents using a tail artery cannula during awake imaging, and (3) measuring Ca2+ signals from synthetic and genetically encoded Ca2+ indicators in astrocytes. This method will facilitate acute two-photon fluorescence imaging in awake, active mice and help link cellular events within the neurovascular unit to behavior.

Activation of the habenula complex evokes autonomic physiological responses similar to those associated with emotional stress.

Neurons in the lateral habenula (LHb) discharge when an animal anticipates an aversive outcome or when an expected reward is not forthcoming, contributing to the behavioral response to aversive situations. So far, there is little information as to whether the LHb also contributes to autonomic physiological responses, including increases in body temperature (emotional hyperthermia) that are integrated with defensive behaviors. Vasoconstriction in cutaneous vascular bed and heat production in brown adipose tissue (BAT) both contribute to emotional hyperthermia. Our present study determines whether stimulation of the LHb elicits constriction of the tail artery and BAT thermogenesis in anesthetized Sprague–Dawley rats. Disinhibition of neurons in LHb with focal microinjections of bicuculline (1 nmol in 100 nl, bilaterally) acutely increased BAT temperature (+0.6 ± 0.1°C, n = 9 rats, P < 0.01) and reduced tail artery blood flow (by 88 ± 4%, n = 9 rats, P < 0.01). Falls in mesenteric blood flow, simultaneously recorded, were much less intense. The pattern of BAT thermogenesis and cutaneous vasoconstriction elicited by stimulating the habenula is similar to the pattern observed during stress-induced emotional hyperthermia, suggesting that the habenula may be important in this response.

Modulatory effect of sodium nitroprusside and 8Br-cGMP on mastoparan-7 induced contraction

I n t r o d u c t i o n . Mastoparan-7 activates G-protein and stimulates apoptosis, but in smooth muscle cells leads to increase in perfusion pressure. Main a i m of this study was to evaluate the modulatory effect of 8Br-cGMP and sodium nitroprusside on vascular smooth muscle contraction induced by direct stimulation of G-protein with mastoparan-7. Ma t e r i a l a n d m e t h o d s . Experiments were performed on isolated and perfused tail artery of Wistar rats. Contraction force in our model was measured by increased level of perfusion pressure with a constant flow. R e s u l t s . Concentration-response curves obtained for mastoparan-7 presented an sigmoidal relation. In presence of SNP and 8Br-cGMP the significant and dose dependent leftward shift with significant reduction in maximal responses was present. Moreover, analyzing function of calcium stores the significant inhibition of influx from both, intra- and extracellular calcium stores was present. C o n c l u s i o n . Results of our experiments suggest that contraction induced by direct activation of G-protein with mastoparan-7 may by effectively inhibited in the presence of donors of nitric oxide such as sodium nitroprusside and in the presence of 8Br-cGMP.

Spinal cord injury increases the reactivity of rat tail artery to angiotensin II.

Studies in individuals with spinal cord injury (SCI) suggest the vasculature is hyperreactive to angiotensin II (Ang II). In the present study, the effects of SCI on the reactivity of the rat tail and mesenteric arteries to Ang II have been investigated. In addition, the effects of SCI on the facilitatory action of Ang II on nerve-evoked contractions of these vessels were determined. Isometric contractions of artery segments from T11 (tail artery) or T4 (mesenteric arteries) spinal cord-transected rats and sham-operated rats were compared 6–7 weeks postoperatively. In both tail and mesenteric arteries, SCI increased nerve-evoked contractions. In tail arteries, SCI also greatly increased Ang II-evoked contractions and the facilitatory effect of Ang II on nerve-evoked contractions. By contrast, SCI did not detectably change the responses of mesenteric arteries to Ang II. These findings provide the first direct evidence that SCI increases the reactivity of arterial vessels to Ang II. In addition, in tail artery, the findings indicate that Ang II may contribute to modifying their responses following SCI.

Evaluation of accuracy of invasive and non-invasive blood pressure monitoring in relation to carotid artery pressure in anaesthetised ponies

Invasive blood pressure measurement (IBP) using peripheral arteries is a commonly used technique in equine anaesthesia, although the accuracy has not been demonstrated. Non-invasive blood pressure monitoring (NIBP) may be indicated for field anesthesia, short procedures and foal anaesthesia. In the present report, the agreement of various IBP and NIBP measuring sites compared to carotid artery pressure was tested in anaesthetised experimental ponies. Six ponies were anaesthetised in lateral recumbency with sevoflurane and received either saline or dexmedetomidine boli followed by constant rate infusion (CRI). Invasive blood pressure measurements were obtained simultaneously from the carotid, facial and metatarsal arteries. NIBP measurements over both median arteries, metatarsal and middle coccygeal arteries were performed in random order. All blood pressure readings obtained were compared to carotid pressure by Bland-Altman analysis. Non-invasive blood pressure measurements had larger bias and poorer limits of agreement compared to IBP measurements. NIBP measurement from the coccygeal artery had the best repeatability and best limits of agreement of all NIBP positions and was not affected by the use of dexmedetomidine. The facial artery had smaller limits of agreement with dexmedetomidine treatment. There was no difference between the facial and metatarsal arteries during dexmedetomidine treatment in MAP and DAP. Systolic arterial pressures from the metatarsal artery showed larger bias and larger limits of agreement compared to facial artery. In conclusion, NIBP measurement from the tail artery is a reliable alternative to direct arterial blood pressure measurement. Both the metatarsal and facial arteries have acceptable agreement with carotid artery pressure so the choice can be based on the logistics of the procedure.

Effects of candesartan, an angiotensin II receptor type I blocker, on atrial remodeling in spontaneously hypertensive rats.

Hypertension‐induced structural remodeling of the left atrium (LA) has been suggested to involve the renin–angiotensin system. This study investigated whether treatment with an angiotensin receptor blocker, candesartan, regresses atrial remodeling in spontaneously hypertensive rats (SHR). Effects of treatment with candesartan were compared to treatment with a nonspecific vasodilatator, hydralazine. Thirty to 32‐week‐old adult male SHR were either untreated (n = 15) or received one of either candesartan cilexetil (n = 9; 3 mg/kg/day) or hydralazine (n = 10; 14 mg/kg/day) via their drinking water for 14 weeks prior to experiments. Untreated age‐ and sex‐matched Wistar‐Kyoto rats (WKY; n = 13) represented a normotensive control group. Untreated SHR were hypertensive, with left ventricular hypertrophy (LVH) compared to WKY, but there were no differences in systolic pressures in excised, perfused hearts. LA from SHR were hypertrophied and showed increased fibrosis compared to those from WKY, but there was no change in connexin‐43 expression or phosphorylation. Treatment with candesartan reduced systolic tail artery pressures of conscious SHR below those of normotensive WKY and caused regression of both LVH and LA hypertrophy. Although hydralazine reduced SHR arterial pressures to those of WKY and led to regression of LA hypertrophy, it had no significant effect on LVH. Notably, LA fibrosis was unaffected by treatment with either agent. These data show that candesartan, at a dose sufficient to reduce blood pressure and LVH, did not cause regression of LA fibrosis in hypertensive rats. On the other hand, the data also suggest that normalization of arterial pressure can lead to the regression of LA hypertrophy.

Hydrogen does not Exert Neuroprotective Effects or Improve Functional Outcomes in Rats After Intracerebral Hemorrhage.

Increasing evidence suggests that reactive oxygen species damage the blood-brain barrier and increase brain edema after intracerebral hemorrhage (ICH). Recently, strong clinical and experimental evidence has shown that hydrogen has potent protective cellular effects in various diseases. However, the effect of hydrogen on ICH remains unclear. The present study investigates whether hydrogen has neuroprotective effects and improves functional outcome in the rat ICH model. ICH model was generated by injecting 50 μl autologous tail artery blood stereotactically into the right caudate nucleus of Sprague-Dawley rats. Rats were randomly divided into four groups: sham, ICH/vehicle, ICH/hydrogen gas, and ICH/hydrogen-rich saline groups. Hydrogen treatment was performed for 3 days. The evaluation of functional outcome was done before, and at 24 and 72 hours after ICH. Hemorrhage volume, immunohistochemistry for 8-hydroxy-2'-deoxyguanosine (8-OHdG), and brain water content were evaluated at 72 hours after ICH. Hydrogen administration reduced the expression of 8-OHdG in the brain, but did not attenuate brain water content or improve functional outcome, regardless of administration route. Hydrogen administration without surgery has no neuroprotective effect in the blood injection rat ICH model.

Identification and functional analysis of a novel tryptophyllin peptide from the skin of the red-eye leaf frog, Agalychnis callidryas.

Amphibian skin has proved repeatedly to be a largely untapped source of bioactive peptides and this is especially true of members of the Phyllomedusinae subfamily of frogs native to South and Central America. Tryptophyllins are a group of peptides mainly found in the skin of members of this genus. In this study, a novel tryptophyllin (TPH) type 3 peptide, named AcT-3, has been isolated and structurally-characterised from the skin secretion and lyophilised skin extract of the red-eye leaf frog, Agalychnis callidryas. The peptide was identified in and purified from the skin secretion by reverse-phase HPLC. MALDI-TOF mass spectrometry and MS/MS fragmentation sequencing established its primary structure as: pGlu-Gly-Lys-Pro-Tyr-Trp-Pro-Pro-Pro-Phe-Leu-Pro-Glu, with a non-protonated molecular mass of 1538.19Da. The mature peptide possessed the canonical N-terminal pGlu residue that arises from post-translational modification of a Gln residue. The deduced open-reading frame consisted of 63 amino acid residues encoding a highly-conserved signal peptide of approximately 22 amino acid residues, an intervening acidic spacer peptide domain, a single AcT-3 encoding domain and a C terminal processing site. A synthetic replicate of AcT-3 was found to antagonise the effect of BK on rat tail artery smooth muscle and to contract the intestinal smooth muscle preparations. It was also found that AcT-3 could dose-dependently inhibit the proliferation of human prostate cancer cell lines after 72h incubation.

Assessing the agonist profiles of the prostacyclin analogues treprostinil and naxaprostene, particularly their DP1 activity

In this study, the inhibitory profiles of the prostacyclin analogues treprostinil and naxaprostene on several isolated smooth muscle preparations have been investigated. Treprostinil was an agonist for prostanoid DP1, EP2 and IP receptors, but not EP4 receptors; its DP1 potency was only 3–4 times less than PGD2 itself. Naxaprostene was much more selective for IP receptors and tended towards partial agonism. Treprostinil is a 13,14-dihydro analogue and the role of conformation around C12–15 in controlling agonist specificity is debated; the synthesis of new analogues is proposed and possible clinical usage discussed. In terms of selective prostanoid antagonists employed, BW-A868C/MK-0524 (DP1), ACA-23 (EP2) and GW-627368 (EP4) were found fit for purpose. However, the IP antagonist RO-1138452 was compromised by α1 and α2-adrenoceptor-mediated contractile activity on rat tail artery and anti-muscarinic activity on mouse trachea. There is a need for IP receptor antagonists with better selectivity and higher affinity.

Comparison of the post-mortem interval on the effect of vascular responses to the activation of ionotropic and metabotropic receptors.

The contractibility of blood vessels depends on their normal structure and the availability of calcium ions; it changes under the influence of numerous contracting and relaxing factors, which control the activities of various pathways of intracellular and intercellular signaling. The main aim of the study was to investigate, by means of perfusion pressure in rat tail arteries, the role of Ca2+ in vascular response to α-1 adrenoceptor activation by phenylephrine (PHE) and Bay K8644 agonist of the L-type calcium channel and caffeine before and after a post-mortem interval (PMI) of 2, 4, 6 and 8 h. A phasic increase of perfusion pressure in rat tail arteries, as induced by PHE or caffeine, in Ca2+-free solutions was used as an indicator of intracellular Ca2+ release through the inositol 1,4,5-triphosphate and ryanodine receptor pathways, respectively. In Ca2+-free-ethylene glycol tetraacetic acid (EGTA)-poly(sodium styrenesulfonate) (PSS) and in Ca2+-EGTA-PSS, the PHE induced elevation of perfusion pressure significantly decreased. Vascular responses to caffeine (20 mmol/1) in Ca2+-free-EGTA-PSS, with an increase of PMI from 2-8 h, did not change significantly. A similar effect was observed with vascular responses to KCl 40 mmol/1 in Ca2+-EGTA-PSS. To confirm whether the inhibitory effect of 2, 4, 6 and 8 h PMI was mediated through the formation of NO, nitro-L-arginine (L-NNA), a potent NO synthase inhibitor, was used. Exposure to L-NNA (10-5 M) blocked the inhibition induced by an increase of PMI. The blocked effects of L-NNA were reversed by L-arginine (10-4 M). In conclusion, these patterns of change in artery responses provide insight into the post-mortem change in the receptor-mediated signaling components in epithelial and smooth muscle cells, and support the further study of post-mortem vascular responses triggered by G protein-coupled receptors (metabotropic) and channel-linked receptors (ionotropic) as potential markers for estimating short and long-term PMIs, respectively.

Hydrogen sulfide upregulates KATP channel expression in vascular smooth muscle cells of spontaneously hypertensive rats.

The study was designed to investigate whether H2S could upregulate expression of KATP channels in vascular smooth muscle cells (VSMCs), and by this mechanism enhances vasorelaxation in spontaneously hypertensive rats (SHR). Blood pressure, vascular structure, and vasorelaxation were analyzed. Plasma H2S was detected using polarographic sensor. SUR2B and Kir6.1 expressions were detected in VSMCs of SHR and in A7r5 cells as well as primarily cultured ASMCs using real-time PCR, western blot, immunofluorescence, and confocal imaging. Nuclear translocation of forkhead transcription factors FOXO1 and FOXO3a in ASMCs was detected using laser confocal microscopy, and their binding activity with SUR2B and Kir6.1 promoters was examined by chromatin immunoprecipitation. SHR developed hypertension at 18weeks. They showed downregulated vascular SUR2B and Kir6.1 expressions in association with a decreased plasma H2S level. H2S donor, however, could upregulate vascular SUR2B and Kir6.1 expressions, causing a left shift of the vasorelaxation curve to pinacidil and lowered tail artery pressure in the SHR. Also, H2S antagonized endothelin-1 (ET-1)-inhibited KATP expression in A7r5 cells and cultured ASMCs. Mechanistically, H2S inhibited ET-1-stimulated p-FOXO1 and p-FOXO3a expressions (inactivated forms), but increased their nuclear translocation and the ET-1-inhibited binding of FOXO1 and FOXO3a with Kir6.1 and SUR2B promoters in ASMCs. Hence, H2S promotes vasorelaxation of SHR, at least in part, through upregulating the expression of KATP subunits by inhibiting phosphorylation of FOXO1 and FOXO3a, and stimulating FOXO1 and FOXO3a nuclear translocation and their binding activity with SUR2B and Kir6.1 promoters. H2S increased vascular SUR2B and Kir6.1 expression of SHR, promoting vasorelaxation. H2S antagonized ET-1-inhibited KATP expression in A7r5 cells and cultured ASMCs. H2S inhibited ET-1-induced FOXO1 and FOXO3a phosphorylation in ASMCs. H2S promoted FOXO1 and FOXO3a nuclear translocation and binding with target gene promoters.