Experimental monitoring of hepatic glucose,lactate, and glutamate metabolism by microdialysis during surgical preparation of the liver hilus

Mechanical liver manipulation can lead to hepatic microcirculation (MC) impairment. The pathobiochemical relevance of this phenomenon is not fully understood. Microdialysis (MD) allows a quantification of metabolic products in interstitial fluid, thus enabling analysis of the hepatic metabolic state during changes of liver perfusion. The aim of the study was to quantify the functional effects of standardized surgical liver preparation both on liver metabolism and microperfusion. Two groups of animals (pigs, n = 25) were formed: In the trial group (TG; n = 13) the liver was mobilized, followed by hilar preparation. In the control group (CG; n = 12) mobilization of the liver without hilar dissection was performed. Surgical manipulation was followed by an observation in both groups. Hepatic interstitial glucose, lactate, and glutamate concentrations were detected by MD and liver MC by thermodiffusion. During liver mobilization MC decreased significantly in both groups (TG; 86.7 +/- 2.0 to 73.4 +/- 2.3 ml/100 g min; and CG; 88.3 +/- 3.1 to 71.9 +/- 2.2 ml/100 g/min). In the trial group levels decreased further during hilar preparation reaching minimal values of 65.6 +/- 2.8. After preparation MC recovered to baseline. Glucose, lactate, and glutamate concentrations increased significantly during liver mobilization in the trial (glucose; 0.52 +/- 0.13 to 0.88 +/- 0.19 mmol/L; lactate; 0.34 +/- 0.07 to 0.54 +/- 0.07 mmol/L; glutamate; 34.5 +/- 3.6 to 52.6 +/- 8.0 micromol/L) and control group (glucose; 0.58 +/- 0.06 to 0.95 +/- 0.13 mmol/L; lactate; 0.30 +/- 0.06 to 0.49 +/- 0.07 mmol/L; glutamate; 32.9 +/- 2.36 to 56.1 +/- 5.12 micromol/L). Throughout hilus preparation maximum values could be measured in TG (glucose; 1.69 +/- 0.34; lactate; 0.90 +/- 0.18; glutamate; 63.5 +/- 7.2). After termination of mobilization or preparation baseline concentrations were reached again. MD allows monitoring of metabolic changes in hepatic parenchyma. Surgical liver preparation leads to changes of intrahepatic glucose, lactate, and glutamate levels (without alterations of parameters in systemic plasma) along with hepatic MC impairment. Reconstitution of hepatic MC was accompanied by rapid normalization of metabolic parameters. By measuring specific parameters, MD could prove to be of use for functional assessment of metabolic effects due to MC disturbances.     

Effect of fenfluramine-induced increases in serotonin release on [18F]MPPF binding: a continuous infusion PET study in conscious monkeys

[(18)F]MPPF is a selective and reversible antagonist to the serotonin-1A (5-HT(1A)) receptor. The aim of the present study was to investigate whether the binding of [(18)F]MPPF is sensitive to increases in 5-HT levels. We used the 5-HT releasing agent and reuptake inhibitor fenfluramine (FEN) to increase the concentration of 5-HT. [(18)F]MPPF binding was assessed using positron emission tomography (PET) in conscious monkeys. Possible effects of blood flow on ligand binding were excluded by using a bolus-infusion paradigm. Control scans were obtained to assess the state of ligand equilibrium. FEN (5 or 10 mg/kg, i.v.) was administered between 90 and 130 min after the start of the [(18)F]MPPF infusion. The binding potential (BP) was calculated for an early interval (30 min preceding FEN administration) and late interval (20-50 min after administration of FEN). Microdialyses results showed a 20- and 35-fold increase in extracellular 5-HT levels in the prefrontal cortex after injection of FEN at a dose of 5 mg/kg and 10 mg/kg respectively. However, despite these large increases in 5-HT levels, no differences in BP were found between the control and FEN scans. These results may imply that the majority of 5-HT(1A) receptors is in the low affinity state in the living brain.     

Effect of epinephrine on epidural, intrathecal, and plasma pharmacokinetics of ropivacaine and bupivacaine in sheep

BACKGROUND: Local vasoconstriction induced by epinephrine added to epidural local anaesthetics has been shown to improve their quality and duration of action in several clinical reports. There are several assumptions on the mechanisms. This study was designed to evaluate the influence of epinephrine on transmeningeal uptake of epidurally administered ropivacaine and bupivacaine by measuring local anaesthetic concentrations in the epidural and intrathecal spaces and in plasma. METHODS: Ropivacaine (50 mg) and bupivacaine (30 mg) were administered epidurally in sheep with and without epinephrine (75 microg). A microdialysis technique was used to simultaneously measure epidural and intrathecal drug concentrations. Resulting dialysate and plasma concentrations were used to calculate pharmacokinetic parameters for ropivacaine and bupivacaine. RESULTS: Co-administration of epinephrine decreased epidural clearance for ropivacaine [0.6 (sd 0.1) vs 0.4 (0.1) ml min(-1)] but not significantly for bupivacaine [1.2 (0.4) vs 0.8 (0.3) ml min(-1)]. The resultant increase in epidural area under the concentration-time curves (31% for ropivacaine and 52% for bupivacaine) was also observed in the intrathecal space (21% increase for ropivacaine and 37% for bupivacaine). There was no significant influence of epinephrine on ropivacaine plasma pharmacokinetics. Plasma Cmax for bupivacaine was decreased. CONCLUSIONS: These results show that epinephrine decreases the clearance and distribution processes involved in epidural disposition of ropivacaine and bupivacaine, leading to an increased uptake into the intrathecal space with an apparent more pronounced effect for bupivacaine.     

Neuromonitoring

The monitoring of critically ill brain injured patients has become increasingly complex. Several techniques are now available for global and regional brain monitoring that provide assessment of cerebral perfusion, oxygenation and metabolic status, and early warning of impending brain hypoxia/ischaemia. Developments in multimodality monitoring have enabled a move away from rigid physiological target setting to an individually tailored, patient-specific approach to the management of acute brain injury. Multimodal monitoring generates large and complex datasets, and systems that analyse and present information in a user-friendly format at the bedside are essential to maximize its clinical relevance. This review describes current neuromonitoring techniques used during the intensive care management of acute brain injury.     

Purines Change at Acupoints along the Pericardium Meridian in Healthy and Myocardial Ischemic Rats

Objective: To quantify the purine concentrations of the acupoints along the pericardium and nonpericardium meridians under healthy and myocardial ischemia conditions to investigate the relationship between acupoint purine change and body functional status in rats. Methods: A total of 70 rats underwent an operation for myocardial ischemia, while 40 of them survived. They were randomly assigned to the following 5 subgroups: Neiguan (PC 6), Quze (PC 3), Tianquan (PC 2), Quchi (LI 11), and Jianyu (LI 15). Simultaneously, another 40 healthy rats were also randomized into the same 5 subgroups as the control group. The tissue fluids at the acupoints were collected by microdialysis for 30 min. Subsequently, the concentration of adenosine triphosphate (ATP), adenosine diphosphate (ADP), adenosine monophosphate (AMP), and adenosine (ADO) were quantified using the high-performance liquid chromatography method. Results: Compared with the healthy group, the ADO at PC 6 (P=0.012), PC 3 (P=0.038), PC 2 (P=0.024), and LI 15 (P=0.042) obviously increased in the model group, while no significant difference was observed at LI 11 (P=0.201). However, ATP, ADP, and AMP manifested no significant changes in these areas, except for ATP at LI 15 (P=0.036). Conclusions: Myocardial ischemia could induce an increase in ADO at acupoints of the upper arm and shoulder area, suggesting that the body functional status could affect the responsiveness of acupoints. The status of these acupoints could be pathogenically activated by disease, and distribution following some specific courses.     

Dobutamine compensates deleterious hemodynamic and metabolic effects of vasopressin in the splanchnic region in endotoxin shock

BACKGROUND: Vasopressin is a potent vasopressor in septic shock, but it may impair splanchnic perfusion. We compared the effects of vasopressin alone and in combination with dobutamine on systemic and splanchnic circulation and metabolism in porcine endotoxin shock. METHODS: Twelve pigs were randomized to receive either vasopressin (VASO, n = 6) or vasopressin in combination with dobutamine (DOBU, n = 6) during endotoxin shock (E. coli endotoxin infusion). Endotoxin infusion rate was increased to induce hypotension after which vasoactive drugs were started. We aimed to keep systemic mean arterial pressure (MAP) >70 mmHg by vasopressin; the goal of dobutamine infusion was to prevent decrease in cardiac output often associated with vasopressin infusion. Regional blood flows, oxygen delivery and consumption, arterial and regional lactate concentrations were measured. RESULTS: Mean arterial pressure >70 mmHg was achieved in both the VASO and DOBU groups. After the primary decrease of cardiac output by vasopressin, systemic blood flow remained stable in vasopressin-treated animals. However, vasopressin as a monotherapy decreased portal venous blood flow. This was prevented by dobutamine. Vasopressin also induced splanchnic lactate release and arterial hyperlactatemia, which were not observed when dobutamine was combined with vasopressin. CONCLUSION: Dobutamine prevents adverse hemodynamic and metabolic effects of vasopressin in septic shock.     

A novel Na+‐Independent alanine‐serine‐cysteine transporter 1 inhibitor inhibits both influx and efflux of D‐Serine

NMDA receptor dysfunctions are hypothesized to underlie the pathophysiology of schizophrenia, and treatment with D‐serine (D‐Ser), an NMDA receptor coagonist, may improve the clinical symptoms of schizophrenia. Thus, upregulating the synaptic D‐Ser level is a novel strategy for schizophrenia treatment. Na⁺‐independent alanine‐serine‐cysteine transporter 1 (asc‐1) is a transporter responsible for regulating the extracellular D‐Ser levels in the brain. In this study, we discovered a novel asc‐1 inhibitor, (+)‐amino(1‐(3,5‐dichlorophenyl)‐3,5‐dimethyl‐1H‐pyrazol‐4‐yl)acetic acid (ACPP), and assessed its pharmacological profile. ACPP inhibited the D‐[³H]Ser uptake in human asc‐1‐expressing CHO cells and rat primary neurons with IC₅₀ values of 0.72 ± 0.13 and 0.89 ± 0.30 μM, respectively. In accordance with the lower asc‐1 expression levels in astrocytes, ACPP did not inhibit D‐Ser uptake in rat primary astrocytes. In a microdialysis study, ACPP dose dependently decreased the extracellular D‐Ser levels in the rat hippocampus under the same conditions in which the asc‐1 inhibitor S‐methyl‐L‐cysteine (SMLC) increased it. To obtain insights into this difference, we conducted a D‐[³H]Ser efflux assay using asc‐1‐expressing CHO cells. ACPP inhibited D‐[³H]Ser efflux, whereas SMLC increased it. These results suggest that ACPP is a novel inhibitor of asc‐1. © 2016 Wiley Periodicals, Inc.     

微透析技术在药动-药效学结合研究中的应用

微透析技术能直接、有效地对作用部位细胞外液中的内源性及外源性化合物进行持续检测,是药动-药效学结合研究的重要工具,具有不可替代的作用及广阔的应用前景。本文概述了微透析技术的基本原理及特点,并重点介绍了其在药动-药效学结合研究中的应用。     

微透析技术探针回收率的影响因素研究进展

微透析技术是近年来发展起来的动态生物取样技术，具有“活体、微创、实时、高效”等特点，其与现代分析技术联用，实现了连续取样和动态测定，可进行微量的定性、定量分析。微透析探针回收率的准确校正，是测定生物体中待测组分确切浓度的关键步骤，可提高大分子、难溶性物质的回收率，使微透析的应用更为广泛。本文对微透析探针回收率的影响因素、校正方法以及近年来提高回收率所取得的进展做一综述。     

改变大脑5-羟色胺水平对戊四氮点燃大鼠癫癎形成过程的影响

目的研究西酞普兰(提高脑内5-羟色胺水平)、利血平(耗竭5-羟色胺)对癫癎形成过程的影响,探讨大脑5-羟色胺(5-HT)水平变化在癫癎形成的作用。方法大鼠随机分为对照组、戊四氮组、西酞普兰组、利血平组;用西酞普兰和利血平干预后,再用戊四氮点燃形成慢性癫癎,在点燃过程,进行海马脑电记录和微透析取样,在体观察48只自由活动大鼠行为、脑电和发作间期5-羟色胺能神经递质的变化。结果 (1)在点燃早期,西酞普兰组发作潜伏期延长,发作程度轻和点燃时间延长,发作死亡率低,与戊四氮组比较差异有显著性(P<0.05);点燃后,西酞普兰组诱发发作潜伏期、发作程度的变化与戊四氮组比较无统计学意义。点燃初期,西酞普兰组大鼠的海马5-HT水平升高,5-HT转化率(5-HIAA/5-HT)降低,与对照组和戊四氮组比较有显著性差异(P<0.05);点燃后,西酞普兰组5-HT水平降低,与PTZ组比较无统计学意义;与对照组比较有显著性差异(P<0.05);西酞普兰组5-HIAA水平在点燃过程逐渐降低与对照组比较,差异有统计学意义(P<0.01),与戊四氮组比较差异无统计学意义;点燃后,5-HT转化率(5-HIAA/5-HT)变化与戊四氮组和对照组比较,无统计学意义。(2)在点燃初期,利血平组发作潜伏期缩短,发作程度重,点燃时间缩短,发作死亡率高,与对照组、戊四氮组比较,差异有统计学意义,(P<0.05);点燃后,发作情况与戊四氮组比较,有统计学意义。点燃初期,利血平组5-HT水平降低与戊四氮组和对照组比较,差异有统计学意义(P<0.05),点燃后,利血平组5-HT水平逐渐下降与对照组比较差异有统计学意义(P<0.05),和PTZ组差异无统计学意义;点燃过程中,5-HIAA水平,利血平组呈逐日下降趋势,与对照组比较差异有统计学意义(P<0.01),与PTZ组差异无统计学意义;点燃期间和维持点燃期利血平组5-HT转化率(5-HIAA/5-HT)变化,与对照组和戊四氮组比较,差异无统计学意义。结论提高大脑5-HT水平,戊四氮点燃大鼠癫癎形成所需点燃时间显著延长;在戊四氮点燃大鼠早期,提高大脑5-HT水平,癫癎发作程度明显减轻;但提高大脑5-HT水平,未能最终阻断戊四氮点燃的癫癎形成;癫癎形成后,提高大脑5-HT水平未能抑制癫癎发作。降低大脑5-HT水平,戊四氮点燃大鼠癫癎形成所需点燃时间显著缩短;在戊四氮点燃大鼠期间,降低大脑5-HT水平,癫癎发作程度明显加重;降低大脑5-HT水平,可加速戊四氮点燃癫癎形成。