Projetos geot��rmicos para usos diretos em Portugal Continental: tipologias e viabilidade econ��mica

Os aproveitamentos geot��rmicos t��m vindo a aumentar significativamente em todo o mundo, sendo os Estados Unidos da Am��rica, o maior produtor desta energia proveniente do interior da Terra, com cerca de 3.187 MW de capacidade instalada. Portugal tem capacidade instalada total de 29 MW, no entanto no que se refere ao aproveitamento de ���alta entalpia���, isto ��, o aproveitamento geot��rmico para produ����o el��trica, apenas se encontra no arquip��lago dos A��ores, na ilha de S. Miguel, onde est��o instaladas e em funcionamento duas centrais geot��rmicas com a pot��ncia total de 23 MW, com produ����o de energia de 185 GWh. Em Portugal Continental, n��o se consegue produzir energia el��trica devido ��s temperaturas existentes, restringindo esta utiliza����o apenas ao aproveitamento de baixa entalpia (m��ximo de 76 ��C). Este aproveitamento normalmente �� feito em cascata, segundo, predominando o aquecimento de ��guas sanit��rias, climatiza����o, e para termas, usando ��guas termominerais. Para a explora����o deste recurso renov��vel, �� necess��rio conhecer a hidrogeologia do pa��s, e relacion��-la com a fractura����o, e acidentes tect��nicos. Portugal Continental, est�� divido em quatros partes distintas a n��vel hidrogeol��gico, o Maci��o Antigo, a Orla Ocidental, a Bacia Tejo-Sado e a Orla Meridional. Qualquer aproveitamento geot��rmico em Portugal ter�� de atender a estas caracter��sticas, potenciando tamb��m, novas explora����es geot��rmicas orientadas para as pessoas, respeitando os valores sociais, culturais e ambientais. Neste contexto, existem alguns complexos geot��rmicos em funcionamento, outros abandonados, e muitos outros em estudo para uma breve aplica����o. Um exemplo de sucesso no aproveitamento do calor geot��rmico, �� o complexo de Chaves, que foi evoluindo desde 1985, at�� aos dias de hoje, continuando em explora����o e em expans��o para um melhor servir da popula����o local. A exist��ncia de dois furos, e brevemente dum terceiro, servem para o abastecimento duma piscina, dum hotel, das termas, e da balneoterapia. Devido �� riqueza a n��vel das temperaturas, dos caudais, e ao n��vel das necessidades energ��ticas existentes, este complexo apresenta um tempo de retorno de investimento de cerca de 7 anos, o que �� geralmente considerado para investimentos para fins p��blicos, como �� o caso. No ��mbito das investiga����es agora realizadas, foi constatado que estes projetos suportam a cobertura de alguma incerteza hidrogeol��gica, dada a importante procura existente.

Rapid automated method for on-site determination of sulfadiazine in fish farming: a stainless steel veterinary syringe coated with a selective membrane of PVC serving as a potentiometric detector in a flow-injection-analysis system

Sulfadiazine is an antibiotic of the sulfonamide group and is used as a veterinary drug in fish farming. Monitoring it in the tanks is fundamental to control the applied doses and avoid environmental dissemination. Pursuing this goal, we included a novel potentiometric design in a flow-injection assembly. The electrode body was a stainless steel needle veterinary syringe of 0.8-mm inner diameter. A selective membrane of PVC acted as a sensory surface. Its composition, the length of the electrode, and other flow variables were optimized. The best performance was obtained for sensors of 1.5-cm length and a membrane composition of 33% PVC, 66% onitrophenyloctyl ether, 1% ion exchanger, and a small amount of a cationic additive. It exhibited Nernstian slopes of 61.0 mV decade-1 down to 1.0��10-5 mol L-1, with a limit of detection of 3.1��10-6 mol L-1 in flowing media. All necessary pH/ionic strength adjustments were performed online by merging the sample plug with a buffer carrier of 4-(2-hydroxyethyl)-1-piperazineethanesulfonic acid, pH 4.9. The sensor exhibited the advantages of a fast response time (less than 15 s), long operational lifetime (60 days), and good selectivity for chloride, nitrite, acetate, tartrate, citrate, and ascorbate. The flow setup was successfully applied to the analysis of aquaculture waters. The analytical results were validated against those obtained with liquid chromatography���tandem mass spectrometry procedures. The sampling rate was about 84 samples per hour and recoveries ranged from 95.9 to 106.9%.

Trimethoprim-selective electrodes with molecularly imprinted polymers acting as ionophores and potentiometric transduction on graphite solid-contact

This work proposes a new biomimetic sensor material for trimethoprim. It is prepared by means of radical polymerization, having trimethylolpropane trimethacrylate as cross-linker, benzoyl peroxide as radicalar iniciator, chloroform as porogenic solvent, and methacrylic acid and 2-vinyl pyridine as monomers. Different percentages of sensor in a range between 1 and 6% were studied. Their behavior was compared to that obtained with ion-exchanger quaternary ammonium salt (additive tetrakis(p-chlorophenyl)borate or tetraphenylborate). The effect of an anionic additive in the sensing membrane was also tested. Trimethoprim sensors with 1% of imprinted particles from methacrylic acid monomers showed the best response in terms of slope (59.7 mV/decade) and detection limit (4.01 �� 10��� 7 mol/L). These electrodes displayed also a good selectivity towards nickel, manganese aluminium, ammonium, lead, potassium, sodium, iron, chromium, sulfadiazine, alanine, cysteine, tryptophan, valine and glycine. The sensors were not affected by pH changes from 2 to 6. They were successfully applied to the analysis of water from aquaculture.

Selective recognition in potentiometric transduction of amoxicillin by molecularly imprinted materials

The indiscriminate use of antibiotics in food-producing animals has received increasing attention as a contributory factor in the international emergence of antibiotic-resistant bacteria (Woodward in Pesticide, veterinary and other residues in food, CRC Press, Boca Raton, 2004). Numerous analytical methods for quantifying antibacterial residues in edible animal products have been developed over years (Woodward in Pesticide, veterinary and other residues in food, CRC Press, Boca Raton, 2004; Botsoglou and Fletouris in Handbook of food analysis, residues and other food component analysis, Marcel Dekker, Ghent, 2004). Being Amoxicillin (AMOX) one of those critical veterinary drugs, efforts have been made to develop simple and expeditious methods for its control in food samples. In literature, only one AMOX-selective electrode has been reported so far. In that work, phosphotungstate:amoxycillinium ion exchanger was used as electroactive material (Shoukry et al. in Electroanalysis 6:914���917, 1994). Designing new materials based on molecularly imprinted polymers (MIPs) which are complementary to the size and charge of AMOX could lead to very selective interactions, thus enhancing the selectivity of the sensing unit. AMOX-selective electrodes used imprinted polymers as electroactive materials having AMOX as target molecule to design a biomimetic imprinted cavity. Poly(vinyl chloride), sensors of methacrylic acid displayed Nernstian slopes (60.7 mV/decade) and low detection limits (2.9 �� 10���5 mol/L). The potentiometric responses were not affected by pH within 4���5 and showed good selectivity. The electrodes were applied successfully to the analysis of real samples.

Projeto de uma unidade de produ����o de biodiesel num reator ultrass��nico pela via supercr��tica

A concretiza����o deste est��gio na INCBIO teve como principal objetivo o projeto e dimensionamento de uma unidade de produ����o de biodiesel por transesterifica����o n��ocatal��tica num reator ultrass��nico com condi����es supercr��ticas de press��o e temperatura. Com vista �� concretiza����o do trabalho, iniciou-se a realiza����o do estudo do estado da arte relativo �� produ����o de biodiesel, com particular enfoque na produ����o de biodiesel por via catal��tica e por via supercr��tica e na produ����o de biodiesel com uso de tecnologia ultrass��nica. Conclui-se que nenhum estudo contempla a combina����o simult��nea da produ����o de biodiesel por via supercr��tica atrav��s da tecnologia ultrass��nica. Este estudo do estado da arte permitiu ainda definir as condi����es de temperatura, press��o e r��cio m��ssico (250 ��C, 95 bar e 1:1 respetivamente) a considerar no projeto da unidade de produ����o de biodiesel deste trabalho. Com base no estudo do estado da arte efetuado e com base nas caracter��sticas da mat��ria procedeu-se �� defini����o do processo de produ����o de biodiesel. Para a defini����o do processo come��ou-se por elaborar o diagrama de blocos do processo (BFD) e o diagrama de fluxo do processo (PFD). Com base nos diagramas e na composi����o da mat��ria-prima, procedeu-se �� quantifica����o dos reagentes (metanol) com base na estequiometria das rea����es envolvidas e ao c��lculo do balan��o de massa. O balan��o de massa foi calculado com base na estequiometria das rea����es envolvidas e foi tamb��m calculado atrav��s do software de simula����o ASPEN PLUS. Ap��s o c��lculo do balan��o de massa elaborou-se o diagrama de tubula����o e instrumenta����o (P&ID), que cont��m todos os equipamentos, v��lvulas, instrumenta����o e tubagens existentes na unidade. Ap��s a defini����o do processo e c��lculo do balan��o de massa procedeu-se ao dimensionamento mec��nico e c��lculo hidr��ulico dos tanques, tubagem, bombas, permutador de calor, reator ultrass��nico, v��lvulas de controlo e instrumenta����o de acordo com as normas ASME. Nesta fase do trabalho foram consultados diversos fornecedores poss��veis para a compra de todo o material necess��rio. O dimensionamento mec��nico e c��lculo hidr��ulico efetuados permitiram, entre outras informa����es relevantes, obter as dimens��es necess��rias �� constru����o do layout e �� elabora����o do desenho 3D. Com os resultados obtidos e desenhos elaborados, �� poss��vel avan��ar com a constru����o da unidade, pelo que pode-se inferir que o objetivo de projetar uma unidade de produ����o de biodiesel num reator ultrass��nico com condi����es supercr��ticas foi alcan��ado. Por fim, efetuou-se uma an��lise econ��mica detalhada que possibilita a compara����o de uma unidade de produ����o de biodiesel por via catal��tica (unidade de produ����o da INCBIO) com a unidade de produ����o de biodiesel num reator ultrass��nico com condi����es supercr��ticas (unidade projetada neste trabalho). Por quest��es de confidencialidade, n��o foram revelados maior parte dos resultados da an��lise econ��mica efetuada. No entanto, conclui-se que os custos de constru����o da unidade de produ����o de biodiesel num reator ultrass��nico com condi����es supercr��ticas s��o mais baixos cerca de 35 a 40%, quando comparados com os custos de constru����o da unidade de produ����o de biodiesel por via catal��tica, evidenciando assim que a combina����o em simult��neo das condi����es supercr��ticas com a tecnologia ultrass��nica possibilita a diminui����o dos custos de produ����o.

Otimiza����o energ��tica �� sec����o das malhas

A presente disserta����o realizada na empresa Continental-Ind��stria T��xtil do Ave, S.A., teve como objetivo a otimiza����o energ��tica da sec����o das malhas. Esta sec����o divide-se em duas ��reas, a tricotagem e a ramulagem. Os artigos produzidos diferem no seu peso espec��fico, composi����o e condi����es de opera����o, sendo os artigos A, B e C compostos por poli��ster e termofixados a 190��C e os artigos D e E compostos por poli��ster e algod��o, com uma temperatura de opera����o de 205��C. Numa primeira etapa estudou-se o funcionamento da m��quina de termofixa����o ��� a r��mula ��� que opera em trabalho cont��nuo a 40 m/min. Esta m��quina tem incorporado um permutador de calor, que aquece o ar fresco de entrada com os gases de exaust��o das estufas. Posteriormente efetuou-se o levantamento energ��tico de cada artigo, para as ��reas de tricotagem e ramulagem. Verificou-se que os artigos D e E, pela sua constitui����o, s��o os que apresentam um consumo espec��fico superior, em tep/ton. Entre as v��rias utilidades consumidas (g��s natural, eletricidade e ar comprimido) o g��s natural representa mais de 50% do consumo de energia total necess��rio para a produ����o de cada artigo. Ap��s a completa an��lise aos consumos energ��ticos da r��mula, foram realizados ensaios de otimiza����o, tendo-se conclu��do que a diminui����o do caudal de exaust��o pode atingir valores de poupan��a anual de g��s natural na ordem dos 3.000 ���. Com o objetivo de avaliar o consumo de g��s natural, n��o sendo poss��vel a realiza����o experimental, foram feitas simula����es com base em altera����es na corrente de entrada de ar fresco no permutador. Foi tamb��m estudada a possibilidade de isolamento e revestimento t��rmico da conduta exterior, projetada para o reaproveitamento do ar dos compressores, tendo-se obtido um or��amento de 2.500 ���. Admitindo-se uma gama de temperaturas entre os 40��C e os 60��C, com um caudal de insufla����o de 30%, obteve-se um payback entre os 0,97 e os 3,28 anos. Numa segunda fase admitiu-se uma temperatura m��dia de 50��C, aumentando o caudal de insufla����o at�� 100%. O per��odo de retorno obtido variou entre os 0,33 e os 1,38 anos, podendo as poupan��as anuais atingirem os 7.600 ���.

Development of a thermoelectric generator for the exhaust of a vehicle

Disserta����o de mestrado integrado em Engenharia Mec��nica

Particle transport in fouling caused by kaolin-water suspensions on copper tubes

Particulate fouling tests were carried out using kaolin-water suspensions flowing through an annular heat exchanger with a copper inner tube. The flow rate was changed from test to test, but the fluid temperature and pH, as well as the particle concentration, were maintained constant. In the lower range of fluid velocities (<0.5 m/s), the deposition process seemed to be controlled by mass transfer. The corresponding experimental transport fluxes were compared to the predictions obtained with several models, showing that diffusion governed particle transport. The absolute values of the mass transfer fluxes and their dependences on the Reynolds number were satisfactorily predicted by some of the models.

The design and development of heat extraction technologies for the utilisation of compost thermal energy

A composting Heat Extraction Unit (HEU) was designed to utilise waste heat from decaying organic matter for a variety of heating application The aim was to construct an insulated small scale, sealed, organic matter filled container. In this vessel a process fluid within embedded pipes would absorb thermal energy from the hot compost and transport it to an external heat exchanger. Experiments were conducted on the constituent parts and the final design comprised of a 2046 litre container insulated with polyurethane foam and kingspan with two arrays of qualpex piping embedded in the compost to extract heat. The thermal energy was used in horticultural trials by heating polytunnels using a radiator system during a winter/spring period. The compost derived energy was compared with conventional and renewable energy in the form of an electric fan heater and solar panel. The compost derived energy was able to raise polytunnel temperatures to 2-3��C above the control, with the solar panel contributing no thermal energy during the winter trial and the electric heater the most efficient maintaining temperature at its preset temperature of 10��C. Plants that were cultivated as performance indicators showed no significant difference in growth rates between the heat sources. A follow on experiment conducted using special growing mats for distributing compost thermal energy directly under the plants (Radish, Cabbage, Spinach and Lettuce) displayed more successful growth patterns than those in the control. The compost HEU was also used for more traditional space heating and hot water heating applications. A test space was successfully heated over two trials with varying insulation levels. Maximum internal temperature increases of 7��C and 13��C were recorded for building U-values of 1.6 and 0.53 W/m2K respectively using the HEU. The HEU successfully heated a 60 litre hot water cylinder for 32 days with maximum water temperature increases of 36.5��C recorded. Total energy recovered from the 435 Kg of compost within the HEU during the polytunnel growth trial was 76 kWh which is 3 kWh/day for the 25 days when the HEU was activated. With a mean coefficient of performance level of 6.8 calculated for the HEU the technology is energy efficient. Therefore the compost HEU developed here could be a useful renewable energy technology particularly for small scale rural dwellers and growers with access to significant quantities of organic matter

The appraisal of anaerobic digestion in Ireland to develop improved designs and operational practice

Mesophilic Anaerobic Digestion treating sewage sludge was investigated at five full-scale sewage treatment plants in Ireland. The anaerobic digestion plants are compared and evaluated in terms of design, equipment, operation, monitoring and management. All digesters are cylindrical, gas mixed and heated Continuously Stirred Tank Reactors (CSTR), varying in size from 130m3 to 800m3. Heat exchanger systems heat all digesters. Three plants reported difficulties with the heating systems ranging from blockages to insufficient insulation and design. Exchangers were modified and replaced within one year of operation at two plants. All but one plant had Combined Heat and Power (CHP) systems installed. Parameter monitoring is a problem at all plants mainly due to a lack of staff and knowledge. The plant operators consider pH and temperature the most important parameters to be measured in terms of successful monitoring of an anaerobic digester. The short time taken and the ease at which pH and temperature can be measured may favour these parameters. Three laboratory scale pilot anaerobic digesters were operated using a variety of feeds over at 144-day period. Two of the pilots were unmixed and the third was mechanically mixed. As expected the unmixed reactors removed more COD by retention of solids in the digesters but also produced greater quantities of biogas than the mixed digester, especially when low solids feed such as whey was used. The mixed digester broke down more solids due to the superior contact between the substrate and the biomass. All three reactors showed good performance results for whey and sewage solids. Scum formation occurred giving operational problems for mixed and unmixed reactors when cattle slurry was used as the main feed source. The pilot test was also used to investigate which parameters were the best indicators of process instability. These trials clearly indicated that total Volatile Fatty Acid (VFA) concentrations was the best parameter to show signs of early process imbalance, while methane composition in the biogas was good to indicate possible nutrient deficiencies in the feed and oxygen shocks. pH was found to be a good process parameter only if the wastewater being treated produced low bicarbonate alkalinities during treatment.

Estudi d'impacte ac��stic de les obres d'un intercanviador de metro

En el territori del Barcelon��s les obres han estat a l���ordre del dia. Abans de l���inici de la crisi es van encetar i programar nombroses obres tan d���immobles com de grans infraestructures com la que aqu�� es presenta: un intercanviador de metro. L���alta densitat demogr��fica d���aquesta regi�� ha fet que aquests treballs realitzats a les obres siguin poc compatibles amb el benestar i la salut de la poblaci��. Un dels principals factors causants del malestar als ve��ns ��s el soroll. Mitjan��ant estudis de modelitzaci�� ac��stica, com el realitzat en aquest projecte, es pret��n preveure i evitar que l���afecci�� ac��stica derivada de les obres sigui perjudicial per la persona per tal de compatibilitzar al m��xim possible les feines de l���obra amb el benestar general. Mitjan��ant el programa de monitoritzaci�� ac��stica Cadna���A i nombroses mesures ac��stiques in situ s���ha pogut preveure la futura afecci�� sonora de 6 fases d���obra considerades com les m��s sorolloses i s���han proposat un seguit de mesures preventives i/o correctores per tal d���assolir uns nivells ac��stics assequibles amb la legislaci�� vigent.

NEDD4-2 and salt-sensitive hypertension.

PURPOSE OF REVIEW: NEDD4-2 is an ubiquitin-protein ligase that was originally identified as an interactor of the epithelial Na+ channel (ENaC); this interaction is defective in Liddle's syndrome, causing elevated ENaC activity and salt-sensitive hypertension. In this review we aim to highlight progress achieved in recent years demonstrating that NEDD4-2 is involved in the control of Na+ transporters that are different from ENaC, but which also play a role in salt-sensitive hypertension. RECENT FINDINGS: It has been shown that NEDD4-2 interacts with ubiquitylates and negatively regulates the thiazide-sensitive NCC (Na+,Cl- -cotransporter), both in vitro and in vivo in inducible, nephron-specific Nedd4-2 knockout mice. Moreover, evidence has been provided that NEDD4-2 is also involved in the regulation of human NHE3 (Na+,H+-exchanger 3) and NKCC2 (Na+,K+,2Cl- -cotransporter 2). SUMMARY: The emerging role of NEDD4-2 in the regulation of different Na+ transporters along the nephron and the identification of human polymorphisms in the NEDD4-2 gene (Nedd4L) related to salt-sensitive hypertension makes this ubiquitin-protein ligase an interesting target for the development of antihypertensive drugs.

Spontaneous NA+ transients in individual mitochondria of intact astrocytes.

Mitochondria in intact cells maintain low Na(+) levels despite the large electrochemical gradient favoring cation influx into the matrix. In addition, they display individual spontaneous transient depolarizations. The authors report here that individual mitochondria in living astrocytes exhibit spontaneous increases in their Na(+) concentration (Na(mit)(+) spiking), as measured using the mitochondrial probe CoroNa Red. In a field of view with approximately 30 astrocytes, up to 1,400 transients per minute were typically detected under resting conditions. Na(mit)(+) spiking was also observed in neurons, but was scarce in two nonneural cell types tested. Astrocytic Na(mit)(+) spikes averaged 12.2 +/- 0.8 s in duration and 35.5 +/- 3.2 mM in amplitude and coincided with brief mitochondrial depolarizations; they were impaired by mitochondrial depolarization and ruthenium red pointing to the involvement of a cation uniporter. Na(mit)(+) spiking activity was significantly inhibited by mitochondrial Na(+)/H(+) exchanger inhibition and sensitive to cellular pH and Na(+) concentration. Ca(2+) played a permissive role on Na(mit)(+) spiking activity. Finally, the authors present evidence suggesting that Na(mit)(+) spiking frequency was correlated with cellular ATP levels. This study shows that, under physiological conditions, individual mitochondria in living astrocytes exhibit fast Na(+) exchange across their inner membrane, which reveals a new form of highly dynamic and localized functional regulation.

Nitric oxide reduces Cl- absorption in the mouse cortical collecting duct through an ENaC-dependent mechanism.

Since nitric oxide (NO) participates in the renal regulation of blood pressure, in part, by modulating transport of Na(+) and Cl(-) in the kidney, we asked whether NO regulates net Cl(-) flux (JCl) in the cortical collecting duct (CCD) and determined the transporter(s) that mediate NO-sensitive Cl(-) absorption. Cl(-) absorption was measured in CCDs perfused in vitro that were taken from aldosterone-treated mice. Administration of an NO donor (10 &#956;M MAHMA NONOate) reduced JCl and transepithelial voltage (VT) both in the presence or absence of angiotensin II. However, reducing endogenous NO production by inhibiting NO synthase (100 &#956;M N(G)-nitro-l-arginine methyl ester) increased JCl only in the presence of angiotensin II, suggesting that angiotensin II stimulates NO synthase activity. To determine the transport process that mediates NO-sensitive changes in JCl, we examined the effect of NO on JCl following either genetic ablation or chemical inhibition of transporters in the CCD. Since the application of hydrochlorothiazide (100 &#956;M) or bafilomycin (5 nM) to the perfusate or ablation of the gene encoding pendrin did not alter NO-sensitive JCl, NO modulates JCl independent of the Na(+)-dependent Cl(-)/HCO3(-) exchanger (NDCBE, Slc4a8), the A cell apical plasma membrane H(+)-ATPase and pendrin. In contrast, both total and NO-sensitive JCl and VT were abolished with application of an epithelial Na(+) channel (ENaC) inhibitor (3 &#956;M benzamil) to the perfusate. We conclude that NO reduces Cl(-) absorption in the CCD through a mechanism that is ENaC-dependent.

The congenital soidum diarrhea and Spint2: from the molecules to the disease

La diarrh��e cong��nitale de sodium est une maladie g��n��tique tr��s rare. Les enfants touch��s par cette maladie pr��sentent une diarrh��e aqueuse s��v��re accompagn��e d'une perte f��cale de sodium et bicarbonates causant une d��shydratation hyponatr��mique et une acidose m��tabolique. Des analyses g��n��tiques ont identifi�� des mutations du g��ne Spint2 comme cause de cette maladie. Le g��ne Spint2 code pour un inhibiteur de s��rine prot��ase transmembranaire exprim�� dans divers ��pith��liums tels que ceux du tube digestif ou des tubules r��naux. Le r��le physiologique de Spint2 n'est pas connu. De plus, aucun partenaire physiologique de Spint2 n'a ��t�� identifi�� et le m��canisme d'inhibition par Spint2 nous est peu connu. Le but de ce projet est donc d'obtenir de plus amples informations concernant la fonction et le r��le de Spint2 dans le contexte de la diarrh��e cong��nitale de sodium, cela afin de mieux comprendre la physiopathologie des diarrh��es et peut-��tre d'identifier de nouvelles cibles th��rapeutiques. Un test fonctionnel dans les ovocytes de Xenopus a identifi�� les s��rine prot��ases transmembranaires CAPI et Tmprssl3 comme potentielles cibles de Spint2 dans la mesure o�� ces deux prot��ases n'��taient plus bloqu��es par le mutant de Spint2 Y163C qui est associ�� avec la diarrh��e cong��nitale de sodium. Des exp��riences fonctionnelles et biochimiques plus pouss��es sugg��rent que l'inhibition de Tmprssl3 par Spint2 est le r��sultat d'une interaction complexe entre ces deux prot��ines. Les effets des s��rine prot��ases transmembranaires sur l'��changeur Na+-H+ NHE3, qui pourrait ��tre impliqu�� dans la pathogen��se de la diarrh��e cong��nitale de sodium ont aussi ��t�� test��s. Un clivage sp��cifique de NHE3 par la s��rine prot��ase transmembranaire Tmprss3 a ��t�� observ�� lors d'exp��riences biochimiques. Malheureusement, la pertinence physiologique de ces r��sultats n'a pas pu ��tre ��valu��e in vivo, ��tant donn�� que le mod��le de souris knockout conditionnel de Spint2 que nous avons cr���� ne montrait une r��duction de l'expression de Spint2 que de 50% et aucun ph��notype. En r��sum��, ce travail met en ��vidence deux nouveaux partenaires possibles de Spint2, ainsi qu'une potentielle r��gulation de NHE3 par des s��rine prot��ases transmembranaires. Des exp��riences suppl��mentaires faites dans des mod��les animaux et lign��es cellulaires sont requises pour ��valuer la pertinence physiologique de ces donn��es et pour obtenir de plus amples informations au sujet de Spint2 et de la diarrh��e cong��nitale de sodium. - The congenital sodium diarrhea is a very rare genetic disease. Children affected by this condition suffer from a severe diarrhea characterized by watery stools with a high fecal loss of sodium and bicarbonates, resulting in hyponatremic dehydration and metabolic acidosis. Genetic analyses have identified mutations in the Spint2 gene as a cause of this disease. The spint2 gene encodes a transmembrane serine protease inhibitor expressed in various epithelial tissues including the gastro-intestinal tract and renal tubules. The physiological role of Spint2 is completely unknown. In addition, physiological partners of Spint2 are still to be identified and the mechanism of inhibition by Spint2 remains elusive. Therefore, the aim of this project was to get insights about the function and the role of Spint2 in the context of the congenital sodium diarrhea in order to better understand the pathophysiology of diarrheas and maybe identify new therapeutic targets. A functional assay in Xenopus oocytes identified the membrane-bound serine proteases CAPI and Tmprssl3 as potential targets of Spint2 because both proteases were no longer inhibited by the mutant Spint2 Y163C that has been associated with the congenital diarrhea. Further functional and biochemical experiments suggested that the inhibition of Tmprssl3 by Spint2 occurs though a complex interaction between both proteins. The effects of membrane-bound serine proteases on the Na+-H+ exchanger NHE3, which has been proposed to be involved in the pathogenesis of the congenital sodium diarrhea, were also tested. A specific cleavage of NHE3 by the membrane-bound serine protease Tmprss3 was observed in biochemical experiments. Unfortunately, the physiological relevance of these results could not be assessed in vivo since the conditional Spint2 knockout mouse model that we generated showed a reduction in Spint2 expression of only 50% and displayed no phenotype. Briefly, this work provides two new potential partners of Spint2 and emphasizes a putative regulation of NHE3 by membrane-bound serine proteases. Further work done in animal models and cell lines is required to assess the physiological relevance of these results and to obtain additional data about Spint2 and the congenital diarrhea.