Transportadores de iones en pulmón: Uso como dianas terapéuticas / Ion transporters in the lungs. Use as therapeutic targets

Los canales de cloruros, de sodio, de bicarbonato y los de agua (aquaporinas) se coordinan para mantener la cubierta líquido superficial de las vías respiratorias, que es necesaria para el aclaramiento mucociliar. El mecanismo general para el transporte de electrolitos y agua depende principalmente de la expresión diferencial y distribución de los transportadores y bombas de iones. Los iones y el agua se mueven a través de las vía paracelular o transcelular. La ruta transcelular del transporte de electrolitos requiere un transporte activo (dependiente de ATP) o pasivo (siguiendo gradientes electroquímicos) de iones. La ruta paracelular es un proceso pasivo que está controlado, en última instancia, por los gradientes electroquímicos transepiteliales predominantes. La fibrosis quística es una enfermedad hereditaria que se produce por mutaciones en el gen que codifica la proteína reguladora de la conductibilidad transmembrana de la fibrosis quística (CFTR) que actúa como un canal de cloro y cumple funciones de hidratación del líquido periciliar y mantenimiento del pH luminal. La disfunción del canal de cloro en el epitelio respiratorio determina una alteración en las secreciones bronquiales, con aumento de su viscosidad y alteración de la depuración mucociliar y que asociado a procesos infecciosos puede conducir a daño pulmonar irreversible. La disfunción del CFTR, también se ha visto implicado en la patogénesis de la pancreatitis aguda, en la enfermedad pulmonar obstructiva crónica y la hiperreactividad en el asma. Existen fármacos que aprovechan los mecanismos fisiológicos en el transporte de iones, con un objetivo terapéutico.

The chloride channels, sodium and bicarbonate channels, and aquaporin water channels are coordinated to maintain the airway surface liquid that is necessary for mucociliary clearance. The general mechanism for the transport of electrolytes and fluids depends mainly on the differential expression and distribution of ion transporters and pumps. Ions and water move through the paracellular or transcellular pathways. The transcellular route of electrolyte transport requires an active transport (dependent on ATP) or passive (following electrochemical gradients) of ions. The paracellular pathway is a passive process that is ultimately controlled by the predominant transepithelial electrochemical gradients. Cystic fibrosis is a hereditary disease that is produced by mutations in the gene that encode cystic fibrosis transmembrane conductance regulatory protein (CFTR) that acts as a chloride channel and performs functions of hydration of periciliary fluid and maintenance of luminal pH. The dysfunction of the chlorine channel in the respiratory epithelium determines an alteration in the bronchial secretions, with an increase in its viscosity and alteration of the mucociliary clearance and that associated with infectious processes can lead to irreversible lung damage. CFTR dysfunction has also been implicated in the pathogenesis of acute pancreatitis, chronic obstructive pulmonary disease, and bronchial hyperreactivity in asthma. There are drugs that exploit physiological mechanisms in the transport of ions with a therapeutic objective.

Expression of myo-inositol cotransporters in the sciatic nerve and dorsal root ganglia in experimental diabetes

The transport of myo-inositol is the main mechanism for the maintenance of its high intracellular levels. We aimed to measure the mRNA and protein levels of myo-inositol cotransporters in the sciatic nerve (SN) and dorsal root ganglia (DRG) during experimental diabetes. Streptozotocin-induced (STZ; 4, 8, and 12 weeks; 65 mg/kg; ip) diabetic rats (DB) and age-matched euglycemic (E) rats were used for the analysis of mRNA and protein levels of sodium myo-inositol cotransporters 1, 2 (SMIT1, SMIT2) or H+/myo-inositol cotransporter (HMIT). There was a significant reduction in the mRNA levels for SMIT1 in the SN and DRG (by 36.9 and 31.0%) in the 4-week DB (DB4) group compared to the E group. SMIT2 was not expressed in SN. The mRNA level for SMIT2 was up-regulated only in the DRG in the DB4 group. On the other hand, the protein level of SMIT1 decreased by 42.5, 41.3, and 44.8% in the SN after 4, 8, and 12 weeks of diabetes, respectively. In addition, there was a decrease of 64.3 and 58.0% of HMIT in membrane and cytosolic fractions, respectively, in the SN of the DB4 group. In the DRG, there was an increase of 230 and 86.3% for SMIT1 and HMIT, respectively, in the DB12 group. The levels of the main inositol transporters, SMIT1 and HMIT, were greatly reduced in the SN but not in the DRG. SMIT-1 was selectively reduced in the sciatic nerve during experimental STZ-induced diabetes.

Co-localization and interaction of organic anion transporter 1 with caveolin-2 in rat kidney

The organic anion transporters (OAT) have recently been identified. Although the some transport properties of OATs in the kidney have been verified, the regulatory mechanisms for OAT's functions are still not fully understood. The rat OAT1 (rOAT1) transports a number of negatively charged organic compounds between the cells and their extracellular milieu. Caveolin (Cav) also plays a role in membrane transport. Therefore, we investigated the protein-protein interactions between rOAT1 and caveolin-2. In the rat kidney, the expressions of rOAT1 mRNA and protein were observed in both the cortex and the outer medulla. With respect to Cav-2, the expressions of mRNA and protein were observed in all portions of the kidney (cortex < outer medulla = inner medulla). The results of Western blot analysis using the isolated caveolae-enriched membrane fractions or the immunoprecipitates by respective antibodies from the rat kidney showed that rOAT1 and Cav-2 co-localized in the same fractions and they formed complexes each other. These results were confirmed by performing confocal microscopy with immunocytochemistry using the primary cultured renal proximal tubular cells. When the synthesized cRNA of rOAT1 along with the antisense oligodeoxynucleotides of Xenopus Cav-2 were co-injected into Xenopus oocytes, the [14C]p-aminohippurate and [3H]methotrexate uptake was slightly, but significantly decreased. The similar results were also observed in rOAT1 over-expressed Chinese hamster ovary cells. These findings suggest that rOAT1 and caveolin-2 are co-expressed in the plasma membrane and rOAT1's function for organic compound transport is upregulated by Cav-2 in the normal physiological condition.

Use of sodium transfer tissue biosensor (STTB) for monitoring of marine toxic organism.

A highly sensitive sodium (Na+) transfer tissue biosensor (STTB) was designed using a frog bladder membrane to measure paralytic shellfish poisons (PSP). The STTB consists, of a Na+ electrode covered by the membrane, which was then integrated into a flow-through system for continuous measurements. In the absence of Na+ channel blocker, active transfer of Na+ occurred from inside to outside across the frog membrane. When the STTB was used to measure the Na+ -dependent dissociation of PSP, it was able to detect PSB at a level contained in a single cell. However, 5 fg or higher (100 cells or more) is needed for accurate and reproducible measurements. The toxicity obtained by the STTB was significantly correlated (r = 0.9449) to that determined by the HPLC. Therefore, the simple method of the STTB can be used not only to detect a low level PSP in toxic plankton populations, but also to monitor poisons in shellfish.

El manejo del Ca²+ intracelular por la célula muscular lisa del útero en la rata grávida a término a la que se le hace neuroectomía pélvica / The management of the intracellular Ca²+ through the uterine smooth muscle cell in the pregnant rat at term that suffers a pelvic neurectomy

El músculo liso uterino puede activarse mediante la aplicación de oxitocina y acetilcolina por el aumento del calcio intracelular liberado de los depósitos intracelulares. La neurectomía pélvica (NP) en la rata no interfiere con el embarazo pero ocasiona distocia; en ésta podría estar involucrado dicho manejo del calcio intracelular. Se registró la actividad mecánica de las capas longitudinal y circular del miometrio grávido a término de la rata con inervación intacta (CLI y CCI) y con NP (CLP y CCP) y de la primera capa pero de la rata no grávida (CLNG). La administración de oxitocina a las preparaciones: CLI, CCI, CLP y CCP en Kreps conteniendo alto potasio, bajo calcio y EGTA ocasionaron contracción en las dos primeras (25 y 24mN, respectivamente), mientras que las desnervadas, algunas no reaccionaron, pero otras sí y en éstas, la reacción siempre fue menor (33 por ciento) que las correspondientes a la CLNG (50 por ciento) y a la CLI, siendo máximas en la última (100 por ciento). Estos datos preliminares sugieren que la NP ocasiona disfunción en el manejo del calcio intracelular del músculo liso uterino, de la rata grávida a término y probablemente es un factor para la distocia en la rata con NP

Channels for water flow in epithelia: characteristics and regulation

Pos y Pd, los coeficientes de permeabilidad osmótica y difusiva al agua, de túbulos proximales (TP) de conejo (por cm**2 de membrana celular real, micronm/s) son Pos, 396; Pd, 22; Pos/Pd, 18 (controles). Con paracloromercuribencenosulfonato son Pos, 32; Pd, 10; Pos/Pd, 3. El reactivo de grupos sulfhidrilos ditiotreitol (DTT) revierte la acción del pCMBS. Las energías de activación (Kcal/mol) son Pos, 3.2 (controles); 9.2 (pCMBS); Pd, 5.2 (controles, 9.1 (pCMBS). Por lo tanto, canales acuosos atraviesan la membrana celular control y son cerrados por pCMBS. Las altas permeabilidades de TP (controles) son similares a las de la vejiga urinaria de anfibio (un análogo del túbulo colector, TC), estimulada con hormona antidiurética (ADH) y los valores bajos con pCMBS en TP recuerdan los de TC en reposo (sin ADH). La permeabilidad transcelular puede ser regulada por el estado de grupos sulfhidrilo en TP y por la adición de canales acuosos por la HAD (o su supresión, reposo). En T.P.(a) no-electrólitos extracelulares son arrastrados por el flujo de agua indicando interacción extracelular aguasoluto; (b) la Pos transepitelial es mucho mayor que la transcelualr. Por consiguiente, en adición al flujo transcelular hay flujo paracelular de agua. La permeabilidad en TP se incrementa si la urea luminal es mayor que la sanguínea (en 15-50 mM) y se reduce en la situación inversa. En TD (control) la permeabilidad paracelular es cero. Se incrementa con urea en condición control en TP y muy pequeña en TC...