A chloride conductance exhibiting bicarbonate conductivity in renal inner medullary collecting duct cells.

The anion conductance in primary cultures of rat inner medullary collecting duct cells was studied using perforated-patch whole-cell clamp technique. Depolarizations above 0 mv induced an outward anionic current with a time-dependent activation (Iovt) exhibiting a similar conductivity to Cl- and HCO3-. Iovt showed half-maximal activation around 32 mV with a slope factor of 23 mV, and showed a voltage-dependent activation time course that was well fitted by a sum of two exponential functions. Iovt was potentiated when external pH or external Ca2+ was increased and was blocked by external DIDS, DPC and furosemide. These characteristics of Iovt resemble that of the ClC-K1 channels mediated currents; however, anion substitution studies showed that Iovt exhibits a Br->Cl->I->NO3- conductivity sequence, different from that observed in the ClC-K1 channels-mediated conductance. We suggest that, in inner medullary collecting duct cells, ClC-K channels of an unidentified type give rise to this Cl- and HCO3- conductance. This is the first study of a channel-mediated HCO3- current in kidney tubular cells.

A hyperpolarization-activated, cyclic nucleotide-gated, (Ih-like) cationic current and HCN gene expression in renal inner medullary collecting duct cells.

The cation conductancein primary cultures of rat renal inner medullary collecting duct was studied using perforated-patch and conventional whole cell clamp techniques. Hyperpolarizations beyond -60 mV induced a time-dependent inward nonselective cationic current (I(vti)) that resembles the well-known hyperpolarization-activated, cyclic nucleotide-gated I(h) and I(f) currents. I(vti) showed a half-maximal activation around -102 mV with a slope factor of 25 mV. It had a higher conductance (but, at its reversal potential, not a higher permeability) for K(+) than for Na(+) (gK(+)/gNa(+) = 1.5), was modulated by cAMP and blocked by external Cd(2+) (but not Cs(+) or ZD-7288), and potentiated by a high extracellular K(+) concentration. We explored the expression of the I(h) channel genes (HCN1 to -4) by RT-PCR. The presence of transcripts corresponding to the HCN1, -2, and -4 genes was observed in both the cultured cells and kidney inner medulla. Western blot analysis with HCN2 antibody showed labeling of approximately 90- and approximately 120-kDa proteins in samples from inner medulla and cultured cells. Immunocytochemical analysis of cell cultures and inner medulla showed the presence of HCN immunoreactivity partially colocalized with the Na(+)-K(+)-ATPase at the basolateral membrane of collecting duct cells. This is the first evidence of an I(h)-like cationic current and HCN immunoreactivity in either kidney or any other nonexcitable mammalian cells.

Actividad inmunologica de antigenos miceliales y levaduriformes de diferentes fases de crecimiento de Sporothrix schenckii / Immunological activity of mycelial and yeast antigens from different growth phases of Sporothrix schenckii

Los antígenos metabólicos de Sporothrix schenckii tienen gran utilidad en el diagnóstico y pronóstico de la esporotricosis. La actividad inmunológica de estas moléculas antigénicas, puede variar dependiendo de la cepa utilizada, los medios de cultivo donde crece el hongo, la metodología empleada para su obtención y la morfología del hongo. En el presente trabajo se observa el efecto que tiene la fase de crecimiento de este microorganismo en la actividad inmunológica de antígenos metabólicos, obtenidos de sus formas micelial y levaduriforme. Estos fueron logrados con filtrados de cultivo en diferentes fases de crecimiento y se ensayaron en las pruebas de inmunodifusión (ID) y contrainmunoelectroforesis (CIE) con sueros de pacientes con esporotricosis. A todos se les determinó su contenido proteico y polisacárido. En ambas formas de crecimiento (micelial y levaduriforme) los resultados mostraron un aumento gradual en cuanto a la concentración de polisacáridos de los antígenos durante la fase logarítima de crecimiento, mientras que la concentración de proteínas permaneció constante. La actividad inmunológica mostró un aumento en el número de bandas en la ID y CIE en los antígenos derivados del inicio de la fase estacionaria. Se encontró reacción cruzada en la ID con un suero de paciente con histoplasmosis. Los mejores resultados en ID y CIE se obtuvieron con los antígenos derivados del final de la fase logarítmica de crecimiento