Shunt In Rats Research Articles

Feasibility of Longitudinal Brain PET with Real-Time Arterial Input Function in Rats.

Preclinical dynamic brain PET studies remain hampered by the limitations related to the measurement of the arterial input function (AIF). In this regard, the use of an arterial-venous shunt is a promising method for the generation of real-time AIFs, but its application in longitudinal studies is still impeded by the cumbersome surgeries and high failure rates. We studied the feasibility and reproducibility of double arterial-venous shunt strategies for conducting longitudinal PET studies with real-time AIFs in rats. We studied the feasibility of double arterial-venous shunts in rats in the right/left inguinal region and evaluated inter-animal and intra-animal AIF reproducibilities. Image-derived input function (IDIF) was also obtained for comparison. Dynamic brain FDG PET studies were conducted to estimate kinetic constants and Cerebral Metabolic Rate of Glucose (CMRglc) obtained from standard 2-tissue compartment (2TCM) and Patlak analysis. We showed that longitudinal AIFs from double arterial-venous shunts can be obtained with very high success rate of the surgeries (88%). Our results provided highly reproducible AIF measurements with low inter-animal variabilities (11%) and intra-animal variabilities (5-10%) that were included into the kinetic models, such that longitudinal rate constants and CMRglc can be efficiently estimated without bias associated to the double shunt. Our results indicated that longitudinal IDIF can be also generated without bias along time but showing higher intra-animal uncertainties. We have demonstrated the feasibility and high reproducibility of conducting longitudinal AIF measurements and consequently accurate kinetic modeling using arterial shunt method.

Pulmonary haemodynamic effects of interatrial shunt in heart failure with preserved ejection fraction: a preclinical study.

The aim of this study was to evaluate the effect of the creation of a left-to-right interatrial shunt on pulmonary haemodynamics in rats with heart failure with preserved ejection fraction (HFPEF). An interatrial communication (IAC) was created in 11 healthy rats (Lewis rats) and 11 rats which developed HFPEF (36-week-old spontaneously hypertensive rats [SHR]). Effects of the interatrial shunt were compared to 11 sham-operated Lewis and 11 sham-operated SHR. At 45 days post shunt, strain effect was observed in diastolic function (E/A ratio, p<0.001; isovolumetric relaxation time, p<0.001), left atrial volume (p=0.005) and pulmonary wall shear rate (WSR) (p=0.02) measured by Doppler echo. At sacrifice of the animals (60 days), a strain effect was also noted in elastin density (p=0.003) and eNOS protein expression (p=0.001). Interatrial shunt creation resulted in (i) an increase in pulmonary WSR (p=0.04) and a decrease in left atrial volume (p<0.001), (ii) an increase in elastin density (p<0.005), and (iii) an increase in eNOS protein expression (p=0.03). Creation of a left-to-right atrial shunt in rats with HFPEF was effective in improving pulmonary haemodynamics. In addition, this study provides preliminary evidence of the potential risk of right volume overload and pulmonary hypertension due to atrial shunting.

Modeling of Hypervolemia in Pulmonary Circulation in Rats Changes the Structure of NO-Mediated Relaxation of Pulmonary Arteries.

We analyzed the contribution of soluble guanylate cyclase-dependent pathway into NO-mediated relaxation of pulmonary arteries under conditions of high pulmonary blood flow modeled by creation of carotid artery-jugular vein shunt in rats. Inhibitor of soluble guanylate cyclase suppressed NO-donor induced relaxation was lower in rats with shunt, but dilatation in response to phosphodiesterase V inhibitor did not differ in the sham-operated and shunt groups. Thus, the structure of NO-mediated vasodilatation of pulmonary arteries under conditions of hypervolemia of pulmonary circulation was shifted to soluble guanylate cyclase-independent pathways, whereas intracellular soluble guanylate cyclase-dependent mechanisms of dilatation were in general unchanged.

Abstract W P197: Pulsed Electromagnetic Field Attenuates High Intracranial Pressure Induced Microvascular Shunting in Rats

Introduction: We previously reported that high intracranial pressure (ICP) in rats caused a transition from capillary (CAP) to non-nutritive microvascular shunt (MVS) flow associated with tissue hypoxia and increased blood brain barrier (BBB) permeability. We also showed that pulsed electromagnetic field (PEMF) increases blood flow velocity and tissue oxygenation in the normal rat brain. We hypothesized that PEMF attenuates the detrimental effects of non-nutritive MVS flow induced by high ICP. Methods: Using in vivo 2-photon laser scanning microscopy (2PLSM) over the rat parietal cortex, we studied the effects of PEMF on microvascular blood flow velocity, tissue oxygenation (NADH) and BBB permeability (dye extravasation) before and during 4 hours of elevated ICP. Doppler cortical flow, rectal and cranial temperatures, intracranial and arterial pressures, blood gases and electrolytes were monitored. After baseline imaging at normal ICP (10 mmHg), rats were subjected to intracranial hypertension (30 mmHg) by raising an artificial cerebrospinal fluid reservoir connected to a catheter in the cisterna magna. After control recording at high ICP of 30 mmHg, PEMF was applied for 30 min and imaging was continuously performed for up to 4 hours after the treatment. In control animals PEMF was not applied. Results: PEMF treatment reduced tissue hypoxia as reflected by a decrease in NADH by 14.6±3.7% (n=7 rats per group, mean ± SEM, p&lt;0.05). BBB permeability was also reduced as reflected by reduction of dye extravasation by 17.2±5.4% (p&lt;0.05). This effect was consistent with dilation of arterioles (+4.5±3.2%) and an increase in capillary blood flow velocity (+4.7±3.2%). PEMF did not completely mitigated the gradual increase in MVS flow at high ICP but, as reflected by MVS/capillary ratio, the transition to non-nutritive flow over 4 hours was less steep in the PEMF treated rats compared to the untreated (2.3±1.1 and 3.8±2.1% change per hour, respectively, p&lt;0.05). Conclusions: PEMF reduces tissue hypoxia and BBB degradation by modulating cerebral blood flow topography at intracranial hypertension in a rat brain. PEMF could be an effective treatment for intracranial hypertension after severe cerebral insults.

Angiotensin II and the ERK pathway mediate the induction of leptin by mechanical cyclic stretch in cultured rat neonatal cardiomyocytes

Mechanical cyclic stretch of cardiomyocytes causes cardiac hypertrophy through cardiac-restricted gene expression. Leptin induces cardiomyocyte hypertrophy in response to myocardial stress. In the present study, we evaluated the expression of leptin under cyclic stretch and its role in regulating genetic transcription in cardiomyocytes. Cultured rat neonatal cardiomyocytes were subjected to cyclic stretch, and the expression levels of leptin, ROS (reactive oxygen species) and AngII (angiotensin II) were evaluated. Signal transduction inhibitors were used to identify the pathway of leptin expression. EMSAs were used to identify the binding of leptin/STAT3 (signal transducer and activator of transcription 3) and luciferase assays were used to identify the transcription of leptin in cardiomyocytes. The study also used an invivo model of AV (aortocaval) shunt in rats to investigate leptin, ROS and AngII expression. Leptin and leptin receptor levels increased after cyclic stretch with the earlier expression of AngII and ROS. Leptin expression was suppressed by AngII receptor blockers, an ROS scavenger [NAC (N-acetylcysteine)], an ERK (extracellular-signal-regulated kinase) pathway inhibitor (PD98059) and ERK siRNA. Binding of leptin/STAT3 was identified by EMSAs, and luciferase assays confirmed the transcription of leptin in neonatal cardiomyocytes after cyclic stretch. Increased MHC (myosin heavy chain) expression and [3H]-proline incorporation in cardiomyocytes was detected after cyclic stretch, which were inhibited by leptin siRNA and NAC. The invivo model of AV shunt also demonstrated increased levels of plasma and myocardial leptin, ROS and AngII expression after cyclic stretch. Mechanical cyclic stretch in cardiomyocytes increased leptin expression mediated by the induction of AngII, ROS and the ERK pathway to cause cardiomyocyte hypertrophy. Myocardial hypertrophy can be identified by increased transcriptional activity and an enhanced hypertrophic phenotype of cardiomyocytes.

The efficacy of silver-embedded polypropylene-grafted polyethylene glycol-coated ventricular catheters on prevention of shunt catheter infection in rats

Catheter-related infection is a major complication of ventriculoperitoneal shunt in children. The aim of this study is to determine inflammatory response and the efficacy of polypropylene-grafted polyethylene glycol (PP-g-PEG) copolymer and silver nanoparticle-embedded PP-g-PEG (Ag-PP-g-PEG) polymer-coated ventricular catheters on the prevention of catheter-related infections on a new experimental model of ventriculoperitoneal shunt in rats. Thirty six Wistar albino rats were divided into six groups: group 1, unprocessed sterile silicone catheter-embedded group; group 2, sterile PP-g-PEG-coated catheter group; group 3, sterile Ag-PP-g-PEG-coated catheter group; group 4, infected unprocessed catheter group; group 5, infected PP-g-PEG-coated catheter group; and group 6, infected Ag-PP-g-PEG-coated catheter group, respectively. In all groups, 1-cm piece of designated catheters were placed into the cisterna magna. In groups 4, 5, and 6, all rats were infected with 0.2 mL of 10 × 10(6) colony forming units (CFU)/mL Staphylococcus epidermidis colonies before the catheters were placed. Thirty days after implantation, bacterial colonization in cerebrospinal fluid and on catheter pieces with inflammatory reaction in the brain parenchyma was analyzed quantitatively. Sterile and infected Ag-PP-g-PEG-covered groups revealed significantly lower bacteria colony count on the catheter surface (ANOVA, 0 ± 0, p < 0.001; 1.08 ± 0.18, p < 0.05, respectively). There was moderate inflammatory response in the parenchyma in group 4, but in groups 5 and 6, it was similar to that of the sterile group (ANOVA, 16.33 ± 3.02, p < 0.001; 4.00 ± 0.68, p < 0.001, respectively). The PP-g-PEG, especially Ag-PP-g-PEG polymer-coated ventricular catheters are more effective in preventing the catheter-related infection and created the least inflammatory reaction in the periventricular parenchyma.

Quantification of regional cerebral blood flow in rats using an arteriovenous shunt and micro-PET

Measurement of regional cerebral blood flow (rCBF) in rodents can provide knowledge of pathophysiology of the cerebral circulation, but generally requires blood sampling for analysis during positron emission tomography (PET). We therefore tested the feasibility of using an arteriovenous (AV) shunt in rats for less invasive blood analysis. Six anesthetized rats received [15O]H2O and [15O]CO PET scans with their femoral artery and vein connected by an AV shunt, the activity within which was measured with a germanium ortho-oxysilicate scintillation detector. The [15O]H2O was intravenously injected either at a faster or slower injection rate, while animals were placed either with their head or heart centered in the gantry. The time-activity curve (TAC) from the AV shunt was compared with that from the cardiac ventricle in PET image. The rCBF values were calculated by a nonlinear least-square method using the dispersion-corrected AV-shunt TAC as an input. The AV-shunt TAC had higher signal-to-noise ratio, but also had delay and dispersion compared with the image-derived TAC. The delay time between the AV-shunt TAC and image-based TAC ranged from 11 to 21 s, while the dispersion was estimated to be ∼5 s as a time constant of the dispersion model of exponential function, and both were properly corrected. In a steady-state condition of [15O]CO PET, the blood activity concentration by AV-shunt TAC was also comparable in height with the image-based TAC corrected for partial volume. Whole-brain CBF values measured by [15O]H2O were 0.37±0.04 (mean±S.D.) ml/g/min, partition coefficient was 0.73±0.04 ml/g, and the CBF varied in a linear relationship with partial pressure of carbon dioxide during each scan. The AV-shunt technique allows less invasive, quantitative and reproducible measurement of rCBF in [15O]H2O PET studies in rats than direct blood sampling and radioassay.

Induction of Hypoxia Inducible Factor Rather than Modulation of Collagen Metabolism Improves Cardiac Function and Reduces Left Ventricular Hypertrophy after Aortocaval Shunt in Rats

Introduction: Matrix reorganization and collagen formation have been suggested to be responsible for cardiac remodeling. Recently, Hypoxia Inducible Factors (HIF) has been shown to be also involved. To differentiate the pathogenesis of cardiac remodeling we used two different prolyl 4-hydroxylase (P4H) inhibitors, FG 0041 known for its potential in reducing collagen formation, FG 2216 for its capability to induce HIF. This study was performed to analyze whether the beneficial effects of P4-HI are mediated by induction of HIF or by effects on collagen metabolism. Methods: 8-week-old Wistar rats either had sham operations (n=14) or received Aortocaval Shunt (ACS). From day 2 rats received P4-HI (n=10 for each P4-HI) or vehicle (n=15) by oral gavage. Echocardiography was performed 28 days after ACS; hemodynamic measurements were done after 30 days. Activity of the metalloproteinase 2 and its inhibitor (TIMP), mRNA levels of CTGF, TGFs1, ITGs1 and Collagen I and III protein were measured. Results: After 30 days both HIF was induced in ACS. Treatment with FG 2216 led to an increase of HIF after 30 days compared to FG 0041 and vehicle. Only FG 2216 prevented left ventricular end-diastolic (7.9 mm vs. 9.8 mm; p<0.001) and end-systolic (4.1 vs. 6.0 mm, p<0.001) dilatation and improved left ventricular ejection fraction (85% vs. 74%, p<0.05). Heart weight (1416 ± 71 vs. 1871 ± 51 mg, p<0.001) and lung weight, as a marker for heart failure, (1958 ± 102 mg vs. 2276 ± 105 mg, p<0.05) were lower in the group receiving FG 2216. Collagen protein and metalloproteinase activity accompanying ACS were significantly decreased by FG 0041, but not by FG 2216. Conclusion: Induction of HIF improves cardiac function and reduces cardiac hypertrophy independent of changes in mRNA, collagen protein or metalloproteinase activity in this model of hypertrophy. Thus FG 2216 affects remodeling by directly targeting cardiomyocytes and has negligible effect on collagen production or extracellular matrix composition.

Change of voltage-gate potassium channel in pulmonary arterial smooth muscle cells of pulmonary hypertension induced by left-to-right shunt in rats

To investigate the electrophysiological changes of voltage-gate potassium channel (Kv) of pulmonary arterial smooth muscle cells of pulmonary arterial hypertension in rats induced by left to right shunt, and to analyze the role of Kv during the progress of pulmonary arterial hypertension. Forty male SD rats were randomly divided into three groups, group A (control, n = 10), group B (sham operated only group, n = 10), and group C (PAH model group, n = 20). Mean pulmonary artery pressure (mPAP) and right ventricular hypertrophy index (RVHI) of each rat were measured, single pulmonary artery smooth muscle cell (PASMC) was obtained by acute enzyme separation method (collagenase I plus papain) and the conventional whole-cell patch clamp technique was used to record resting membrane potential (Em), potassium ion current of voltage-gated potassium channel, the I-V curve between each 2 groups was compared, and correlation of each parameter was analyzed. (1) The mPAP and RVHI of group C were significantly higher than those of group A and group B (P < 0.01, respectively). (2) The Em of group C [(-33.00 ± 4.09) mV] was significantly higher than that of group A [(-48.10 ± 4.54) mV] and group B [(-51.11 ± 3.66) mV], P < 0.01. (3) The peak current at +50 mV of voltage-gated potassium channel: in group C [(64.80 ± 8.40) pA/pF], it was significantly lower than that of group A [(120.85 ± 11.66) pA/pF] and group B [(118.03 ± 10.18) pA/pF] (P < 0.01, respectively). None of the parameters showed any significant difference between group A and group B (P > 0.05 for all comparisons). (4) Compared with group A and group B, the I-V curve of group C significantly downward shifted (P < 0.01, respectively). The difference in I-V curve between group A and group B was not significant, P > 0.05. (5) The correlation of resting membrane potential and mPAP and RVHI had significantly positive correlation (P < 0.001, respectively); but the correlation of membrane current, membrane current density and mPAP, RVHI and resting membrane potential had significantly negative correlation (P < 0.001, respectively). During the formation process of left-to-right shunt induced pulmonary arterial hypertension, function of Kv channel was inhibited, suggesting that Kv channel may be the mechanism of pulmonary arterial hypertension induced by left-to-right shunting.

Use of a beta microprobe system to measure arterial input function in PET via an arteriovenous shunt in rats

BackgroundKinetic modeling of physiological function using imaging techniques requires the accurate measurement of the time-activity curve of the tracer in plasma, known as the arterial input function (IF). The measurement of IF can be achieved through manual blood sampling, the use of small counting systems such as beta microprobes, or by derivation from PET images. Previous studies using beta microprobe systems to continuously measure IF have suffered from high background counts.MethodsIn the present study, a light-insensitive beta microprobe with a temporal resolution of up to 1 s was used in combination with a pump-driven femoral arteriovenous shunt to measure IF in rats. The shunt apparatus was designed such that the placement of the beta microprobe was highly reproducible. The probe-derived IF was compared to that obtained from manual sampling at 5-s intervals and IF derived from a left ventricle VOI in a dynamic PET image of the heart.ResultsProbe-derived IFs were very well matched to that obtained by "gold standard" manual blood sampling, but with an increased temporal resolution of up to 1 s. The area under the curve (AUC) ratio between probe- and manually derived IFs was 1.07 ± 0.05 with a coefficient of variation of 0.04. However, image-derived IFs were significantly underestimated compared to the manually sampled IFs, with an AUC ratio of 0.76 ± 0.24 with a coefficient of variation of 0.32.ConclusionsIF derived from the beta microprobe accurately represented the IF as measured by blood sampling, was reproducible, and was more accurate than an image-derived technique. The use of the shunt removed problems of tissue-background activity, and the use of a light-tight probe with minimal gamma sensitivity refined the system. The probe/shunt apparatus can be used in both microprobe and PET studies.

Liver-Assist Device With a Microfluidics-Based Vascular Bed in an Animal Model

This study evaluates a novel liver-assist device platform with a microfluidics-modeled vascular network in a femoral arteriovenous shunt in rats. Liver-assist devices in clinical trials that use pumps to force separated plasma through packed beds of parenchymal cells exhibited significant necrosis with a negative impact on function. Microelectromechanical systems technology was used to design and fabricate a liver-assist device with a vascular network that supports a hepatic parenchymal compartment through a nanoporous membrane. Sixteen devices with rat primary hepatocytes and 12 with human HepG2/C3A cells were tested in athymic rats in a femoral arteriovenous shunt model. Several parenchymal tube configurations were evaluated for pressure profile and cell survival. The blood flow pattern and perfusion status of the devices was examined by laser Doppler scanning. Cell viability and serum protein secretion functions were assessed. Femoral arteriovenous shunt was successfully established in all animals. Blood flow was homogeneous through the vascular bed and replicated native flow patterns. Survival of seeded liver cells was highly dependent on parenchymal chamber pressures. The tube configuration that generated the lowest pressure supported excellent cell survival and function. This device is the first to incorporate a microfluidics network in the systemic circulatory system. The microvascular network supported viability and function of liver cells in a short-term ex vivo model. Parenchymal chamber pressure generated in an arteriovenous shunt model is a critical parameter that affects viability and must be considered in future designs. The microfluidics-based vascular network is a promising platform for generating a large-scale medical device capable of augmenting liver function in a clinical setting.

Sildenafil attenuates pulmonary vascular remodeling and upregulates Kv1.5 mRNA expression in pulmonary hypertension secondary to left-to-right shunt in rats

Sildenafil is a phosphodiesterase-type-5 inhibitor and selectively decreases pulmonary artery pressure. So far, the mechanism underlying sildenafil's effects on pulmonary vascular remodeling and potassium channel activity in pulmonary artery smooth muscle cells (PASMCs) has not been clearly addressed in pulmonary hypertension secondary to increased pulmonary blood flow.

Gender differences in apoptotic signaling in heart failure due to volume overload

This study examined sex differences in the regulation of pro- and anti-apoptotic proteins in cardiac hypertrophy and heart failure due to volume overload induced by arteriovenous (AV) shunt in rats. General characteristics and hemodynamic assessment revealed the presence of cardiac hypertrophy at 4 weeks of AV shunt in male (n = 12) and female (n = 12) rats, whereas heart failure was seen at 16 weeks in male rats only. Although a decrease in apoptosis was seen in hearts of both sexes at 4 weeks, an increase in apoptosis in males and a reduction in the female heart were observed at 16 weeks of AV shunt. Unlike females, increases in the pro-apoptotic proteins, BAX, caspases 3 and 9 were seen in 16 weeks post-AV shunt in male rats. While an increase in phospho-Bad was detected, phospho-Bcl-2 protein was decreased in males. Females showed an increase in only phospho-Bcl-2 protein at 16 weeks post-AV shunt. Ovariectomy (n = 12) abolished the increase in phospho-Bcl-2 protein, but this was restored by treatment with 17-beta estradiol. These data suggest that downregulation of phospho-Bcl-2 and an upregulation of BAX may play a major role in cardiomyocyte apoptosis in heart failure due to volume overload in male rats. Furthermore, upregulation of phospho-Bcl-2 in the heart due to estrogen may confer resistance against cardiomyocyte apoptosis in females.

Pharmacological effects are model specific in animal models of portal hypertension

Pharmacological effects are model specific in animal models of portal hypertension

Plasma redox status is impaired in the portacaval shunted rat – the risk of the reduced antioxidant ability

BackgroundPortacaval shunting in rats produces a reduction of hepatic oxidant scavenging ability. Since this imbalance in hepatic oxidant/antioxidant homeostasis could coexist with systemic changes of oxidant stress/antioxidant status, plasma oxidants and antioxidant redox status in plasma of portacaval shunted-rats were determined.ResultsMale Wistar male: Control (n = 11) and with portacaval shunt (PCS; n = 11) were used. Plasma levels of the oxidant serum advanced oxidation protein products (AOPP), lipid hydroperoxides (LOOH), the antioxidant total thiol (GSH) and total antioxidant status (TAX) were measured. Albumin, ammonia, Aspartate-aminotransferase (AST), Alanine-aminotransferase (ALT), thiostatin and alpha-1-acid glycoprotein (α1-AGP) were also assayed 4 weeks after the operation. AOPPs were significantly higher (50.51 ± 17.87 vs. 36.25 ± 7.21 μM; p = 0.02) and TAX was significantly lower (0.65 ± 0.03 vs. 0.73 ± 0.06 mM; p = 0.007) in PCS compared to control rats. Also, there was hypoalbuminemia (2.54 ± 0.08 vs. 2.89 ± 0.18 g/dl; p = 0.0001) and hyperammonemia (274.00 ± 92.25 vs. 104.00 ± 48.05 μM; p = 0.0001) and an increase of thiostatin (0.23 ± 0.04 vs. 0.09 ± 0.01 mg/ml; p = 0.001) in rats with a portacaval shunt. The serum concentration of ammonia is correlated with albumin levels (r = 0.624; p = 0.04) and TAX correlates with liver weight (r = 0.729; p = 0.017) and albumin levels (r = 0.79; p = 0.007)ConclusionThese findings suggest that in rats with a portacaval shunt a systemic reduction of oxidant scavenging ability, correlated with hyperammonemia, is principally produced. It could be hypothesized, therefore, that the reduced antioxidant defences would mediate a systemic inflammation.

Changes and Distributions of Peptides Derived From Proadrenomedullin in Left-to-Right Shunt Pulmonary Hypertension of Rats

Pulmonary hypertension (PHT) is a common complication of congenital heart disease and the pulmonary vascular structural remodeling because of the high pulmonary blood flow is considered to be the key pathologic process. In the present study the change and distribution of peptides derived from proadrenomedullin in a rat model of PHT caused by a left-to-right shunt were measured to elucidate the mechanism. Twelve weeks after a cervical shunt was established by a cuff technique in an experimental group of rats, the systolic pulmonary artery pressure (sPAP) was measured by catheterization. Morphologic assessment included the measurement of the weight ratio of the right ventricle (RV) to the left ventricle plus septum (LV+SP) and the mean percentage of media wall thickness (MT%) in moderate-sized pulmonary arteries. The distribution of adrenomedullin (ADM), adrenotensin (ADT) and proadrenomedullin N-terminal 20 peptide (PAMP) were measured by immunohistochemical staining. The mRNA expressions of ADM, ADT, PAMP and proADM45-92 were investigated by reverse transcription polymerase chain reaction. The sPAP and the ratios of RV/(LV+SP) and MT% were significantly increased in the experimental rats (p<0.01, and p<0.05). Positive signals (brown granules) of ADM, ADT and PAMP were mainly located in the smooth muscle cells, but the brown granules of PAMP were also located in the tunica adventitia. The levels of ADM and PAMP were significantly increased, while that of ADT was markedly decreased in the Experimental group compared with the Control group (p<0.05 and p<0.01 respectively). The mRNA expression levels of ADM and preADM45-92 were significantly increased in the experimental rats (p<0.01); however, the expression of ADT mRNA was statistically deceased in the Experimental group compared with the Control group (p<0.01). The mRNA expression of PAMP showed no statistical difference between the 2 groups of rats (p>0.05). The change and distribution of peptides derived from proadrenomedullin in PHT caused by a left-to-right shunt in rats is powerful evidence for intramolecular regulation.

Effects of hepatotrophic factors on the liver after portacaval shunt in rats with portal hypertension

Portacaval shunt (PCS) prevent hepatotrophic factors from flowing into the liver, but they enter directly the systemic circulation and worsen liver injury. This study was designed to investigate the effects of hepatotrophic factors through the portal vein on the liver in rats with portal hypertension after portacaval shunt. Intrahepatic portal hypertension (IHPH) was induced by intragastric administration of carbon tetrachloride, and end-to-side PCS was performed. Eight normal rats served as controls, and eight rats with IHPH served as IHPH model (IHPH group). Another 32 rats with IHPH-PCS were randomly subdivided into 4 groups: normal saline (NS) given to 8 rats, hepatocyte growth factor (HGF) 8, insulin (INS) 8, hepatocyte growth factor and insulin (HGF + INS) 8. Hepatotrophic factors were infused into the portal vein through an intravenous catheter. Portal venous pressure (PVP) was measured. The levels of serum alanine aminotransferase (ALT) and aspartate aminotransferase (AST) were tested biochemically and those of hyaluronic acid (HA) and laminin (LN) were measured by radioimmunoassay. Hepatic fibrosis was assessed histologically and the expression of collagens type I and III were detected immunohistochemically. Ultrastructural change of hepatocytes and the number of mitochondria were observed under an electron microscope. The data were compared between groups and subgroups by Student-Newman-Keuls procedure with SPSS10.0. PVP was significantly higher in the IHPH rats than in the control rats (P < 0.05). The levels of serum ALT, AST, HA, and LN, hepatic fibrosis score, the amount of collagen deposition, collagens type I and III increased more significantly in the IHPH group than in the control rats (P < 0.05). The number of mitochondria decreased more significantly in the IHPH rats than in the control rats (P < 0.05). The levels of serum ALT, AST, HA and LN as well as hepatic fibrosis score, the amount of collagen deposition, and the amount of collagens type I and III in the HGF and HGF + INS rats were significantly lower than those in the NS rats (P < 0.05). The damage to hepatocyte ultrastructure was markedly alleviated and the number of mitochondria was increased more significantly in the HGF and HGF + INS rats than in the NS rats under an electron microscope. Perfusion of exogenous hepatotrophic factors through the portal vein can alleviate liver injury, minimize the damage to the ultrastructure of hepatocyte, protect liver function, and lessen hepatic fibrosis in rats with portal hypertension after PCS.

Soy protein diet prevents hypermethioninemia caused by portacaval shunt in rats

In hepatic disorders, abnormal plasma amino acid profiles are observed. In this study, we examined whether soy protein isolate (SPI) improved plasma methionine concentration in the model animals. Portacaval shunt (PCS) increased alanine aminotransferase (ALT) activity and methionine concentration in blood of rats fed a 40% casein diet supplemented with 0.6% methionine (casein-M diet). A 40% SPI diet supplemented with 1.28% methionine (SPI-M diet), which contained the same amount of methionine as that in 40% casein-M diet, normalized plasma ALT activity and methionine level in PCS rats. These effects of a SPI diet may be due to its amino acid composition, since an amino acid mixture diet mimicking a 40% SPI-M diet was also effective to hypermethioninemia of PCS rats. To find key enzymes for the beneficial effect of soy protein, we examined effects of a 40% SPI-M or casein-M diet on the activities of three methionine-metabolizing enzymes in liver of PCS rats. A SPI-M diet stimulated only the activity of cystathionine gamma-lyase, compared with a casein-M diet. A SPI diet has a preventive effect on hypermethioninemia, at least in part, by stimulating cystathionine gamma-lyase activity in liver and may be used for nutritional management of liver disorders with hypermethioninemia.

In vitro and in vivo studies of the novel antithrombotic agent BAY 59-7939—an oral, direct Factor Xa inhibitor

BAY 59-7939 is an oral, direct Factor Xa (FXa) inhibitor in development for the prevention and treatment of arterial and venous thrombosis. BAY 59-7939 competitively inhibits human FXa (K(i) 0.4 nm) with > 10 000-fold greater selectivity than for other serine proteases; it also inhibited prothrombinase activity (IC(50) 2.1 nm). BAY 59-7939 inhibited endogenous FXa more potently in human and rabbit plasma (IC(50) 21 nm) than rat plasma (IC(50) 290 nm). It demonstrated anticoagulant effects in human plasma, doubling prothrombin time (PT) and activated partial thromboplastin time at 0.23 and 0.69 microm, respectively. In vivo, BAY 59-7939 reduced venous thrombosis (fibrin-rich, platelet-poor thrombi) dose dependently (ED(50) 0.1 mg kg(-1) i.v.) in a rat venous stasis model. BAY 59-7939 reduced arterial (fibrin- and platelet-rich) thrombus formation in an arteriovenous (AV) shunt in rats (ED(50) 5.0 mg kg(-1) p.o.) and rabbits (ED(50) 0.6 mg kg(-1) p.o.). Slight inhibition of FXa (32% at ED(50)) reduced thrombus formation in the venous model; to affect arterial thrombosis in the rat and rabbit, stronger inhibition of FXa (74%, 92% at ED(50)) was required. Calculated plasma levels in rabbits at the ED(50) were 14-fold lower than in the rat AV shunt model, correlating with the 14-fold lower IC(50) of FXa inhibition in rabbit compared with rat plasma; this may suggest a correlation between FXa inhibition and antithrombotic activity. Bleeding times in rats and rabbits were not significantly affected at antithrombotic doses (3 mg kg(-1) p.o., AV shunt). Based on these results, BAY 59-7939 was selected for clinical development.

Secretin activation of the apical Na+‐dependent bile acid transporter is associated with cholehepatic shunting in rats†

The role of the cholangiocyte apical Na(+)-dependent bile acid transporter (ASBT) in bile formation is unknown. Bile acid absorption by bile ducts results in cholehepatic shunting, a pathway that amplifies the canalicular osmotic effects of bile acids. We tested in isolated cholangiocytes if secretin enhances ASBT translocation to the apical membrane from latent preexisting intracellular stores. In vivo, in bile duct-ligated rats, we tested if increased ASBT activity (induced by secretin pretreatment) results in cholehepatic shunting of bile acids. We determined the increment in taurocholate-dependent bile flow and biliary lipid secretion and taurocholate (TC) biliary transit time during high ASBT activity. Secretin stimulated colchicine-sensitive ASBT translocation to the cholangiocyte plasma membrane and (3)H-TC uptake in purified cholangiocytes. Consistent with increased ASBT promoting cholehepatic shunting, with secretin pretreatment, we found TC induced greater-than-expected biliary lipid secretion and bile flow and there was a prolongation of the TC biliary transit time. Colchicine ablated secretin pretreatment-dependent bile acid-induced choleresis, increased biliary lipid secretion, and the prolongation of the TC biliary transit. In conclusion, secretin stimulates cholehepatic shunting of conjugated bile acids and is associated with increased cholangiocyte apical membrane ASBT. Bile acid transport by cholangiocyte ASBT can contribute to hepatobiliary secretion in vivo.