No / The aim of this review was to examine whether the measurement of lactate in capillary blood samples using point-of-care handheld analysers corresponds sufficiently closely with arterial and venous whole-blood samples analysed by hospital central laboratory or blood gas analyser to be used interchangeably. A systematic search, informed by focused inclusion/exclusion criteria, was performed using multiple databases up to October 2015. A total of 65 articles were considered to have potential relevance and were evaluated in full text, of which ultimately five articles met all inclusion/exclusion criteria, and a final four were selected after data extraction and quality appraisal. All four studies found a predominantly upward bias in the measurement of lactate in capillary samples tested using a handheld point-of-care device over arterial or venous samples tested by laboratory methods or blood gas analyser. In terms of correlation, there was consensus between the studies that the strength of association between the two methods of measurement was statistically significant. Three studies directly examined the extent of agreement between point-of-care capillary lactate measurements and those of laboratory or blood gas analyser reference determined to ±2 standard deviations; 95% confidence intervals, and report contextually broad limits of agreement, identifying a potential for both over triage and, to a lesser extent, under triage. The findings of the review do not support interchangeable use of handheld fingertip point-of-care lactate measurement with laboratory or blood gas analyser methods in the identification of sepsis.

Dans le cadre de l’évaluation de la néphrotoxicité métabolique du cadmium, nous avons étudié l'effet du chlorure de cadmium (CdCl2) sur la néoglucogenèse dans les tubules rénaux proximaux murins et humains. Les expériences de dose-effets in vitro montrent que le CdCl2 inhibe l’utilisation de lactate et la production de glucose de façon dose-dépendante. En outre, le CdCl2 induit une diminution importante des concentrations cellulaires de l'ATP et des principaux composés contenant des groupements thiols tels que les coenzymes A et le glutathion réduit. Les mesures enzymatiques et de spectroscopie RMN du carbone 13, montrent que le CdCl2 produit dans les tubules rénaux murins et humains respectivement aux concentrations de 10 et 100 μM, une inhibition des flux à travers la lactate déshydrogénase et l'ensemble de la voie de la néoglucogenèse. Nos résultats sont en faveur d’une action inhibitrice directe du cadmium sur les enzymes intervenant dans la voie de la néoglucogenèse. Toutefois, la baisse intracellulaire en ATP, coenzymes A et glutathion, aurait un effet potentialisateur de cette inhibition. Ainsi, cette étude fournit une base biochimique pour une meilleure compréhension des mécanismes cellulaires des tubulopathies proximales survenant chez l'homme suite à une exposition chronique au cadmium. / As part of the assessment of metabolism nephrotoxicity of cadmium, we have studied the effect of cadmium chloride (CdCl2) on gluconeogenesis in isolated mouse and human renal proximal tubules. The dose-response experiments in vitro have shown that CdCl2 inhibits the use of lactate and glucose production in a dose-dependent fashion. Besides, the CdCl2 induced a significant decrease in cellular concentrations of ATP and the main compounds containing thiol groups such as coenzyme A and reduced glutathione. The enzymatic steps and 13C-NMR spectroscopy showed that CdCl2 produced in mouse and human kidney tubules respectively at concentrations of 10 and 100 μM, an inhibition of fluxes through lactate dehydrogenase and the entire gluconeogenic pathway. Our results are in favor of a direct inhibitory action of cadmium on enzymes involved in the gluconeogenic pathway. However, the decrease in intracellular ATP, glutathione and coenzyme A, would have a potentiating effect of this inhibition. Therefore, this study provides a biochemical basis for better understanding the cellular mechanisms of proximal tubular nephropathy occurring in humans following chronic exposure to cadmium.

L'objectif de cette thèse est l'étude du métabolisme de Corynebacterium glutamicum, et de ses potentialités, au cours de procédés aéro-anaérobies. Après une première phase avec apport d'oxygène pour permettre la croissance bactérienne, une phase anaérobie est induite par arrêt de l'aération et réduction de la vitesse d'agitation. Dans ces conditions, le lactate est le principal métabolite produit. La synthèse de ce dernier a été améliorée en jouant, essentiellement, sur le moment de la transition entre les 2 phases. C. glutamicum 2262 peut ainsi produire 27 g/l de lactate en mode discontinu et 55 g/l en mode semi-continu, suite à un arrêt de l'aération lorsque la concentration en biomasse est d'environ 2,6 g/l. Afin d'exploiter la voie de synthèse d'acide lactique chez C. glutamicum pour la production d'éthanol, les gènes PDC et ADH de Zymomonas mobilis ont été exprimés sous le contrôle du promoteur ldhA endogène de C. glutamicum 2262 et d'une souche de C. glutamicum 2262 sans ldhA. Bien que les productivités en éthanol de ces souches aient été relativement faibles, la suppression de ldhA a entraîné des augmentations de la concentration en éthanol d'environ 15 fois. Une stratégie similaire a été utilisée pour la production d'itaconate. Comme dans le cas de l'éthanol, la concentration en itaconate obtenue est demeurée très faible malgré des essais d'amélioration du procédé de mise en oeuvre de la souche productrice d'itaconate / The objective of this work is the study of Corynebacterium glutamicum metabolism, and of its potentialities, during an aero-anaerobic process. After a first phase during which the oxygen was supplied to favor the bacterial growth, the anaerobic phase was induced by the stopping of the oxygen supply and the decreasing of the agitation speed. In these culture conditions, lactate was the main metabolite produced. The production of this organic acid has been increased by modifying the transition time between the aerobic and the anaerobic phases. C. glutamicum 2262 was able to produce up to 27 g/l lactate during a batch process and up to 55 g/l during a fed batch process. To exploit the lactic acid synthesis pathway of C. glutamicum for ethanol production, the PDC and ADH genes from Zymomonas mobilis were expressed under the control of the endogenous promoter of ldhA, in the wild-type strain and in a ldhA-disrupted strain of C. glutamicum 2262. Although the ethanol productivities of these engineered strains were relatively low, the depletion of ldhA resulted in the increases of ethanol final concentration up to 15 times. A similar strategy was applied for the production of itaconate. As previously for the ethanol production, the final concentration of itaconate remained very low despite of some modifications of the process

Neste trabalho são apresentados resultados relacionados a estudos sobre o comportamento eletroquímico do lactato e do peróxido de hidrogênio em diversos eletrodos em meio de diferentes pHs utilizando voltametria cíclica. Também foi investigado o comportamento eletroquímico do peróxido de hidrogênio em eletrodos modificados com filmes de hexacianoferratos utilizando eletrodos de platina e carbono vítreo. A vantagem do uso do CTAB na modificação da superfície de carbono vítreo com Azul da Prússia foi confirmada no que se refere à melhora da sensibilidade e da estabilidade das medidas. Numa etapa posterior desenvolveu-se um biossensor para a determinação de lactato pelo monitoramento de peróxido de hidrogênio produzido na reação catalisada de lactato com oxigênio na presença da enzima lactato oxidase. Nessa etapa, o trabalho consistiu em imobilizar a enzima lactato oxidase na superfície do eletrodo, previamente, modificado com Azul da Prússia, com o auxílio de Nafion®. Após a construção do biossensor e a otimização das condições de análise (pH, quantidade de enzima, volume da amostra e vazão) para obtenção de maior sinal analítico no desenvolvimento do método para a determinação de lactato por análise em fluxo, averiguou-se a repetibilidade das medidas (Clactato = 0,28 mmol L-1) obtendo-se um desvio padrão de 2,2% para 18 repetições. A freqüência analítica foi estimada em 160 injeções por hora com limite de detecção de 0,84 µmol L-1 e linearidade até 0,28 mmol L-1 de lactato. O biossensor foi aplicado na quantificação de lactato em amostras alimentares (cervejas alcoólicas e não alcoólicas) e biológicas (sangue liofilizado e recém coletado). Por fim, realizaram-se estudos envolvendo a variação da concentração de lactato sanguíneo em função da intensidade de atividade esportiva. Os resultados obtidos pelo método proposto foram comparados com aqueles oriundos do uso de método de referência. / Results on the investigation of the electrochemical behavior of lactate and hydrogen peroxide at various electrodic surfaces at different pHs using cyclic voltammetry are presented. Experiments were also carried out with platinum and glassy carbon electrodes modified with hexacyanoferrate films. The advantage of using CTAB in the electrodeposition step of Prussian Blue films onto glassy carbon surfaces was confirmed taking into account both the stability and sensitivity of measurements. The immobilization of lactate oxidase onto glassy carbon electrodes modified with a Prussian Blue layer using Nafion® was performed to fabricate a biosensor for lactate. The biosensor was used in the development of a FIA amperometric method for the determination of lactate. Under optimal operating conditions (pH = 6.9, E = -0.1 V), the linear response of the method was extended up to 0.28 mmol L-1 lactate with a limit of detection of 0.84 µmol L-1. The repeatability of the method for injections of a 0.28 mmol L-1 lactate solution was 2.2 % (n = 18). The analytical frequency was calculated as 160 injections h-1. The usefulness of the method was demonstrated by determining lactate in beer (alcoholic and nonalcoholic beers) and blood samples (lyophilized and freshly collected). Finally, the influence of physical exercise on the blood lactate level was studied. Results obtained by using the proposed amperometric detector compared well with the reference method.

Au cours de ce travail, nous avons recherché l’effet du nitrate et de l’acétate d’uranyle sur des tubules proximaux isolés de reins de souris et de reins humains métabolisant l’un de ses substrats physiologiques, le lactate. Notre étude montre que le nitrate et l’acétate d’uranyle diminuent la gluconéogenèse et le niveau intracellulaire d’ATP de manière dose-dépendante pour des concentrations de l’ordre du millimolaire. Après l’incubation dans un milieu Krebs dépourvu d’ions phosphate en présence de L-[1-13C]-, ou L-[2-13C]-, ou L-[3-13C]lactate, la consommation du substrat et la formation de produits ont été mesurées par des méthodes enzymatiques et par spectroscopie RMN du 13C. En combinant les résultats obtenus par chacune de ces méthodes à l’aide d’un modèle mathématique du métabolisme du lactate, il a pu être montré qu’à la concentration de 3 mM, le nitrate d’uranyle exerce un effet inhibiteur sur les flux enzymatiques de la lactate deshydrogénase (LDH) et de 3 enzymes clés de la gluconéogenèse ; chez la souris et l’homme, les flux sont inhibés respectivement de 14% et 20% (LDH), de 32% et 27% (pyruvate carboxylase), de 36% et 35% (phosphoénolpyruvate carboxykinase) et de 45% et 39% (glucose-6-phosphatase). De plus, une diminution de la quantité de glutathion est observée chez la souris (-36%) et chez l’homme (-12%). Contrairement à ce que l’on attendait, car les ions phosphate pourraient faciliter l’entrée de l’uranium dans la cellule, dans les tubules proximaux murins, l’ajout d’ions phosphate au milieu d’incubation ne semble pas accroître l’inhibition de la gluconéogenèse rénale par le nitrate d’uranyle 3 mM / As part of a study on uranium nephrotoxicity, we investigated the effect of uranyl nitrate and acetate in isolated human and mouse kidney cortex tubules metabolizing the physiological substrate lactate. In the millimolar range, uranyl nitrate and acetate reduced gluconeogenesis and the cellular ATP level in a dose-dependent fashion. After incubation in phosphate-free Krebs-Henseleit medium with 5 mM L-[1-13C]-, ou L-[2-13C]-, ou L-[3-13C]lactate, substrate utilization and product formation were measured by enzymatic and NMR spectroscopic methods. In the presence of 3 mM uranyl nitrate, glucose production and the intracellular ATP content were significantly reduced in both human and mouse tubules. Combination of enzymatic and NMR measurements with a mathematical model of lactate metabolism revealed an inhibition of fluxes through lactate dehydrogenase and the gluconeogenic enzymes in the presence of 3 mM uranyl nitrate; in human and mouse tubules, fluxes were reduced by 20% and 14% (lactate dehydrogenase), 27% and 32% (pyruvate carboxylase), 35% and 36% (phosphoenolpyruvate carboxykinase), and 39% and 45% (glucose-6-phosphatase), respectively. These effects were associated with a 12% and 36 % decrease in the cellular content of glutathione in human and mouse tubules, respectively. Contrary to what expected because phosphate was supposed to facilitate the entry of uranium, the addition of phosphate in the medium did not enhance the inhibitory effect of 3 mM uranyl nitrate on gluconeogenesis in isolated mouse tubules

Le lactate est considéré comme un métabolite déchet depuis de très nombreuses années. Cependant, cette vision semble revisitée depuis quelques temps, avec l'apparition de la notion de glycolyse aérobie et de navettes lactate dans différents types cellulaires (muscle, cerveau et sperme). Concernant le cerveau, des études in vitro, ex vivo et in vivo réalisées ces 20 dernières années ont montré, d'une part, que les astrocytes produisent du lactate et d’autre part que le lactate pouvait être un substrat énergétique pour le système nerveux central (SNC), et plus particulièrement les neurones. Cette notion de navette lactate entre astrocyte et neurone a été proposée pour la première fois en 1994 par Pellerin et Magistretti (ANLS, pour astrocyte-neuron lactate shuttle). Malgré de nombreuses recherches depuis, l'existence d'un transfert net de lactate entre les astrocytes et les neurones n'a toujours pas pu être démontrée in vivo. Dans cet optique, la visualisation de la production de lactate in vivo dans le cerveau activé est essentielle. Le rôle des transporteurs au lactate, MCTs (Monocarboxylate Transporters), dans la détection de ce signal est également un point capital. L’objectif de cette thèse a été de développer la spectroscopie de RMN in vivo localisée dans le cortex somato-sensoriel du rat en condition d’activation cérébrale. Dans un premier temps, un travail de développement a été effectué afin de mettre au point le protocole de stimulation neuronale et d’obtenir un rapport signal sur bruit suffisant pour pouvoir quantifier de façon fiable le lactate. Une fois le protocole établi sur des rats contrôles, l’étude a été réalisée sur des rats modifiés génétiquement et réprimés pour le MCT, soit neuronal, soit astrocytaire. Le but était de déterminer si ce partenaire clef de l’ANLS avait une influence sur les fluctuations de lactate lors de l'activation cérébrale. En plus de la spectroscopie proton in vivo et de l’IRM fonctionnelle, des études de RMN du carbone-13 ont été réalisées ex vivo. Le résultat majeur de cette thèse montre qu’en l’absence du transporteur de lactate neuronal, non seulement on perd l’augmentation de lactate lors de la stimulation cérébrale mais on perd également le signal BOLD sur l’IRMf. Ce résultat suggère, et ce pour la première fois, que l’activité neuronale est fortement dépendante du transporteur au lactate. / Lactate has been considered as a waste metabolite for many years. However, this vision has been reconsidered recently, with the appearance of the notion of aerobic glycolysis and lactate shuttles in different cell types (muscle, brain, and sperm). Concerning the brain, in vitro, ex vivo and in vivo studies carried out over the last 20 years have shown, on the one hand, that astrocytes produce lactate and, on the other hand, that lactate can be an energetic substrate for the central nervous system (CNS), and more particularly neurons. This lactate shuttle between astrocyte and neuron was first proposed in 1994 by Pellerin and Magistretti (called ANLS, for astrocyte-neuron lactate shuttle). Despite many studies since then, the existence of a net transfer of lactate between astrocytes and neurons has still not been demonstrated in vivo. In this regard, visualization of lactate production in vivo in the activated brain is essential. The role of lactate transporters, MCTs (Monocarboxylate Transporters), in detecting this signal is also a key issue. The objective of this thesis was to develop in vivo NMR spectroscopy located in the somato-sensory cortex of rats under brain activation conditions. First, experiments were carried out to develop the neural stimulation protocol and to obtain a sufficient signal-to-noise ratio to be able to quantify lactate. Once the protocol was established on control rats, the study was performed on genetically modified rats and down-regulated for MCT, either neuronal or astrocytic. The aim was to determine whether this key partner of the ANLS has an influence on lactate fluctuations during brain activation. In addition to in vivo proton spectroscopy and functional MRI, carbon-13 NMR studies were performed ex vivo. The major result of this thesis shows that in the absence of the neuronal lactate transporter, not only is the increase in lactate lost during brain stimulation but the BOLD signal on the fMRI is also lost. This result suggests, for the first time, that neural activity is highly dependent on the lactate transporter.

Alternation of indicators of lactate and vegetative systems during heightening of load. Purpose of the investigation was to compare alternation of vegetative systems indicators and blood lactate concentrations and during iterative load heightening. Tasks of the investigation: to compare alternation of vegetative systems indicators during replacement and recovery under different loads in respect of lactate threshold. Eight young healthy males took part in the investigation. Average age of subjects was 21,7 years. Investigation was carried out in Laboratory of Sports Physiology of Lithuania Physical Education Academy. Every subjects has undergone two different investigations: working with veloergometer. One –interval increasing load (3 min of work and 3 min of rest), mill-pedalling frequency – 70 times per minute; the other one – continuous increasing load until subject’s inability to maintain required pedalling frequency. The first load was 70 W. Capillary blood sampling was done from finger at the end of the third min of each load during interval test. While doing continuous increasing load subjects after the warming-up (5 min of work with 50 W of capacity) with the help of the veloergemeter produced continuous load that was heightened by 21 W every minute. Wheeling frequency was 70 times per minute. Starting load was 70 W. Load was continuously heightened until the fatigue, i.e. until the subject was able to take a new load for one minute. During the whole investigation and... [to full text]

[Truncated abstract] In this thesis the role of lactate measurement has been evaluated in intrapartum assessment of fetal wellbeing. Specifically, I have addressed the question of whether fetal lactate measurement is better than the assessment of fetal heart rate patterns or the measurement of pH at predicting fetal brain injury after intrapartum asphyxia. Using an ovine model of repeated umbilical cord occlusion designed to mimic events which may occur during human labour, I have shown that the measurement of fetal lactate levels after repeated cord occlusion is significantly associated with the severity of brain injury after the asphyxial insult. No significant associations were identified with fetal pH measurements or with the duration of decelerative or compound fetal heart rate patterns; however, this is the first study to describe an association between the duration of both increased fetal heart rate variability and fetal heart rate overshoot with the severity of subsequent brain injury. Although no significant association was identified between fetal arterial pressure measured between umbilical cord occlusions and the grade of brain injury, the studies performed in this thesis are the first to show a strong correlation between the duration of specific arterial pressure responses during cord occlusions and the grade of brain injury, accounting for approximately 90% of the variability seen in the severity of injury. The mechanism responsible for the improved ability of lactate measurement to predict fetal brain injury is unknown. It may be because fetal lactate levels are a more stable marker of anaerobic metabolism of glucose than fetal pH levels, which are influenced by both increasing levels of carbon dioxide and anaerobic metabolism of amino-acids and fatty acids. In addition fetal pH levels can be rapidly normalised through placental exchange of carbon dioxide whereas fetal lactate levels are slow to normalise across the placenta as they rely on facilitated diffusion.

Orientador: Antonio de Queiroz Neto / Banca: Guilherme de Camargo Ferraz / Banca: Kênia Cardoso Bícego / Banca: José Arnodson Coelho de Sousa Campelo / Banca: Fernando Queiroz de Almeida / Resumo: Testes que avaliam o desempenho e direcionam a intensidade de treinamento de cavalos, como a aferição do limiar de lactato (LL), são muito úteis na medicina esportiva equina. O presente estudo visa determinar se a velocidade correspondente à concentração de lactato mínimo (VLACMIN) é dependente do protocolo utilizado. A VLACMIN determinada por meio de 5 protocolos (P1 - P5) foram comparados com a velocidade obtida no Teste da Máxima Fase Estável de Lactato (VMAFEL). Oito cavalos árabes treinados foram submetidos a várias sessões para determinação da VMAFEL e comparados com 5 protocolos diferentes. Estes protocolos incluíram um período de aquecimento, seguido de um galope de alta intensidade. Após a corrida, a velocidade foi reduzida para 4 m.s-1. Em P1, P2 e P3 o incremento de velocidade foi fixado em 0,5 m.s -1 e as durações das etapas foram de 3, 5 e 7 min, respectivamente. Em P2, P4 e P5, a duração das etapas foi fixada em 5 min, e o incremento de velocidade foi de 0,5; 1,0; e 1,5 m.s-1, respectivamente. A VLACMIN foi determinada pela aplicação de uma função polinomial de segundo grau. A média e desvio-padrão da VLACMIN dos valores de P1, P2 e P3 e do VMAFEL foram respectivamente: 5,61 ± 0,12 m.s-1; 5,26 ± 0,17 m.s-1; 4,96 ± 0,36 m.s-1; 5,48 ± 0,18 m.s-1 e houve diferença significativa quando comparamos VMAFEL e P3 . A média e desvio-padrão da VLACMIN dos valores de P2 , P4 e P5 e do VMAFEL foram respectivamente: 5,26 ± 0,17 m.s-1; 5,84 ± 0,45 m.s-1; 5,99 ± 0,43 m.s-1; 5,48 ± 0,18 m.s-1, e houve diferença significativa quando comparamos VMAFEL e P5. É possível concluir que a capacidade aeróbia mensurada por meio do método VLACMIN é dependente da duração da etapa, e do incremento da velocidade, nas condições analisadas. / Abstract: Tests to evaluate the performance and direct the intensity of the horses' training, such as the determination of the lactate threshold (LT), hold a great importance in the equestrian sports medicine. The present study aims at determining whether the speed corresponding to the minimum lactate concentration (VLACMIN) is dependent on the protocol used. The VLACMIN determined through 5 protocols (P1 - P5) were compared with the speed obtained in the Lactate Maximum Stable Phase Test (VMFEL). Eight trained Arabian horses underwent several sessions for the VMFEL determination and compared with 5 different protocols. These protocols included a warm-up period, followed by a high-intensity galloping. After the run, the speed was reduced to 4 m.s-1. In P1, P2 and P3 the speed increment was established at 0.5 m.s -1 and the phase durations were of 3, 5 and 7 min, respectively. In P2, P4 and P5, the phases duration was established at 5 min, and the speed increment was of 0.5; 1.0; and 1.5 m.s-1, respectively. The VLACMIN was determined through the application of a second-degree polynomial function. The mean and standard deviation of the VLACMIN of the P1, P2 and P3 values, as well as of the VMFEL, were respectively: 5.61 ± 0.12 m.s-1; 5.26 ± 0.17 m.s-1; 4.96 ± 0.36 m.s-1; 5.48 ± 0.18 m.s-1 and there was significant difference when we compared VMFEL and P3 . The mean and standard deviation of the VLACMIN of the P2 , P4 and P5 values, as well as of the VMFEL, were respectively: 5.26 ± 0.17 m.s-1; 5.84 ± 0.45 m.s-1; 5.99 ± 0.43 m.s-1; 5.48 ± 0.18 m.s-1, and there was significant difference when we compared VMFEL and P5. It is possible to conclude that the aerobic capacity measured through the VLACMIN method is dependent on both the phase duration and the speed increment, in the conditions analyzed. / Doutor

Neste trabalho são apresentados resultados relacionados a estudos sobre o comportamento eletroquímico do lactato e do peróxido de hidrogênio em diversos eletrodos em meio de diferentes pHs utilizando voltametria cíclica. Também foi investigado o comportamento eletroquímico do peróxido de hidrogênio em eletrodos modificados com filmes de hexacianoferratos utilizando eletrodos de platina e carbono vítreo. A vantagem do uso do CTAB na modificação da superfície de carbono vítreo com Azul da Prússia foi confirmada no que se refere à melhora da sensibilidade e da estabilidade das medidas. Numa etapa posterior desenvolveu-se um biossensor para a determinação de lactato pelo monitoramento de peróxido de hidrogênio produzido na reação catalisada de lactato com oxigênio na presença da enzima lactato oxidase. Nessa etapa, o trabalho consistiu em imobilizar a enzima lactato oxidase na superfície do eletrodo, previamente, modificado com Azul da Prússia, com o auxílio de Nafion®. Após a construção do biossensor e a otimização das condições de análise (pH, quantidade de enzima, volume da amostra e vazão) para obtenção de maior sinal analítico no desenvolvimento do método para a determinação de lactato por análise em fluxo, averiguou-se a repetibilidade das medidas (Clactato = 0,28 mmol L-1) obtendo-se um desvio padrão de 2,2% para 18 repetições. A freqüência analítica foi estimada em 160 injeções por hora com limite de detecção de 0,84 µmol L-1 e linearidade até 0,28 mmol L-1 de lactato. O biossensor foi aplicado na quantificação de lactato em amostras alimentares (cervejas alcoólicas e não alcoólicas) e biológicas (sangue liofilizado e recém coletado). Por fim, realizaram-se estudos envolvendo a variação da concentração de lactato sanguíneo em função da intensidade de atividade esportiva. Os resultados obtidos pelo método proposto foram comparados com aqueles oriundos do uso de método de referência. / Results on the investigation of the electrochemical behavior of lactate and hydrogen peroxide at various electrodic surfaces at different pHs using cyclic voltammetry are presented. Experiments were also carried out with platinum and glassy carbon electrodes modified with hexacyanoferrate films. The advantage of using CTAB in the electrodeposition step of Prussian Blue films onto glassy carbon surfaces was confirmed taking into account both the stability and sensitivity of measurements. The immobilization of lactate oxidase onto glassy carbon electrodes modified with a Prussian Blue layer using Nafion® was performed to fabricate a biosensor for lactate. The biosensor was used in the development of a FIA amperometric method for the determination of lactate. Under optimal operating conditions (pH = 6.9, E = -0.1 V), the linear response of the method was extended up to 0.28 mmol L-1 lactate with a limit of detection of 0.84 µmol L-1. The repeatability of the method for injections of a 0.28 mmol L-1 lactate solution was 2.2 % (n = 18). The analytical frequency was calculated as 160 injections h-1. The usefulness of the method was demonstrated by determining lactate in beer (alcoholic and nonalcoholic beers) and blood samples (lyophilized and freshly collected). Finally, the influence of physical exercise on the blood lactate level was studied. Results obtained by using the proposed amperometric detector compared well with the reference method.