Queratodermia palmoplantar epidermolítica de Vörner / Epidermolytic palmoplantar keratoderma of Vörner

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NHA2 is expressed in distal nephron and regulated by dietary sodium

Increased renal reabsorption of sodium is a significant risk factor in hypertension. An established clinical marker for essential hypertension is elevated sodium lithium countertransport (SLC) activity. NHA2 is a newly identified Na+(Li+)/H+ antiporter with potential genetic links to hypertension, which has been shown to mediate SLC activity and H+-coupled Na+(Li+) efflux in kidney-derived MDCK cells. To evaluate a putative role in sodium homeostasis, we determined the effect of dietary salt on NHA2. In murine kidney sections, NHA2 localized apically to distal convoluted (both DCT1 and 2) and connecting tubules, partially overlapping in distribution with V-ATPase, AQP2, and NCC1 transporters. Mice fed a diet high in sodium chloride showed elevated transcripts and expression of NHA2 protein. We propose a model in which NHA2 plays a dual role in salt reabsorption or secretion, depending on the coupling ion (sodium or protons). The identified novel regulation of Na+/H+ antiporter in the kidney suggests new roles in salt homeostasis and disease (AU)

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La acidosis tubular renal distal: una enfermedad hereditaria en la que no se pueden eliminar los hidrogeniones / Distal renal tubular acidosis: a hereditary disease with an inadequate urinary H+ excretion

La acidosis tubular renal distal (ATRD) o ATR tipo I se caracteriza por una disminución en la excreción urinaria de los hidrogeniones H+ y del amonio. En los niños afectados por ATRD hay retraso en el crecimiento, vómito, estreñimiento, falta de apetito, polidipsia y poliuria, nefrocalcinosis, debilidad y hasta parálisis muscular por la hipopotasemia. En este trabajo se resumen los avances en el estudio genético de la ATRD en las poblaciones hasta ahora estudiadas. La ATRD es heterogénea, por lo que también se analizan los transportadores y canales iónicos que se han identificado hasta ahora en las células intercaladas alfa del túbulo colector, y que podrían explicar los casos de ATRD que no se asocian con los genes hasta ahora estudiados. La ATRD puede ser autosómica dominante o autosómica recesiva. La ATRD autosómica recesiva se manifiesta en los primeros meses de vida, cursa con nefrocalcinosis y sordera temprana o tardía. La ATRD autosómica dominante es menos severa y aparece en la adolescencia o en la etapa adulta, y puede o no presentar nefrocalcinosis. En las células intercaladas alfa de los túbulos colectores se lleva a cabo la excreción urinaria de la carga ácida: los ácidos titulables (fosfatos) y el amonio. La ATRD autosómica recesiva se asocia con mutaciones en los genes ATP6V1B1, ATP6V0A4 y SLC4A1, los cuales codifican las subunidades a4 y B1 de la V-ATPasa y el intercambiador de bicarbonato/cloruro AE1, respectivamente. En contraste, la ATRD autosómica dominante se relaciona con mutaciones solo en AE1 (AU)

Distal renal tubular acidosis (dRTA) or RTA type I is characterised by reduced H+ hydrogen ions and ammonium urinary excretion. In children affected by dRTA there is stunted growth, vomiting, constipation, loss of appetite, polydipsia and polyuria, nephrocalcinosis, weakness and muscle paralysis due to hypokalaemia. This work summarises progress made in dRTA genetic studies in populations studied so far. DRTA is heterogeneous and as such, transporters and ion channels are analysed which have been identified in alpha-intercalated cells of the collecting duct, which could explain cases of dRTA not associated with the hitherto studied genes. DRTA can be autosomal dominant or autosomal recessive. Autosomal recessive dRTA appears in the first months of life and progresses with nephrocalcinosis and early or late hearing loss. Autosomal dominant dRTA is less severe and appears during adolescence or adulthood and may or may not develop nephrocalcinosis. In alpha-intercalated cells of the collecting duct, the acid load is deposited into the urine as titratable acids (phosphates) and ammonium. Autosomal recessive dRTA is associated with mutations in genes ATP6V1B1, ATP6V0A4 and SLC4A1, which encode subunits a4 and B1 of V-ATPase and the AE1 bicarbonate/chloride exchanger respectively. By contrast, autosomal dominant dRTA is only related to mutations in AE1 (AU)