RESUMEN
Although abnormalities of calcium and vitamin D metabolism are recognized in children with nephrotic syndrome, longitudinal observations are not available in these patients during periods of relapse and remission. We report observations in 58 children (mean age 10.1 years) with nephrotic syndrome and normal glomerular filtration rate. Hypocalcemia, modest hyperparathyroidism, and strikingly low calcidiol levels were identified during episodes of relapse. Most alterations were transient, and normalized on remission. The plasma concentration of calcitriol, the most active metabolite of vitamin D, was found to be normal in both relapse and remission. In the presence of hypocalcemia and hyperparathyroidism, however, normal plasma calcitriol levels in relapse may be inappropriately low and reflect a state of relative deficiency. Concurrent glucocorticoid therapy did not modify the results. A corollary of our observations is that children with relapsing or protracted nephrotic syndrome are at risk of developing metabolic bone disease, even without impairment of glomerular filtration rate.
Asunto(s)
Calcio/metabolismo , Síndrome Nefrótico/metabolismo , Vitamina D/metabolismo , 25-Hidroxivitamina D 2 , Adolescente , Adulto , Niño , Preescolar , Ergocalciferoles/análogos & derivados , Ergocalciferoles/sangre , Tasa de Filtración Glomerular , Humanos , Hiperparatiroidismo/etiología , Hipocalcemia/etiología , Hipocalcemia/metabolismo , Síndrome Nefrótico/complicaciones , Hormona Paratiroidea/sangre , RecurrenciaRESUMEN
An increase in the osmolarity of the serosal fluid bathing the isolated toad bladder inhibits sodium transport across the preparation. Opposite effects occur with a decrease in serosal Ringer osmolarity. The present experiments investigate the specificity of these osmolar effects by examining the role of extracellular fluid tonicity on the acidification capacity of the isolated Colombian toad bladder. Acidification, estimated by the reversed short-circuit current (RSCC) developing across the Colombian toad bladder in the absence of sodium transport, was stimulated by serosal hypotonicity and inhibited by serosal hypertonicity of acetazolamide. Changes in the mucosal Ringer tonicity had no effect on RSCC. A direct correlation was found between the acidification process and the rate of oxidation of [14C]pyruvate by quarter-bladders exposed to changes in extracellular fluid osmolarity in the presence of amiloride. The osmolar effects on RSCC may result from changes in cell metabolism.