Bicarbonate reabsorption in chronic renal failure.

Bicarbonate reabsorption in chronic renal failure. Bicarbonate reabsorption was studied in dogs before and after induction of renal failure, produced by infarction of one kidney and removal of the contralateral kidney. Glomerular filtration rate and renal plasma flow decreased to 21 and 37% of control values, respectively. Fractional potassium excretion and fractional phosphate excretion increased significantly. Volume expansion resulted in a significant decrease of bicarbonate reabsorption in both control and uremic groups. At comparable levels of fractional chloride excretion, bicarbonate reabsorption was significantly higher in renal failure than in control animals. In the second group of dogs, following induction of renal failure, sodium bicarbonate was given orally in an amount sufficient to neutralize endogenous acid production. Bicarbonate reabsorption was again significantly higher than in control animals. Thyroparathyroidectomy had no effect on bicarbonate reabsorption. Absolute bicarbonate reabsorption and sodium reabsorption were linearly related in control animals and in those in renal failure; the ratio of absolute bicarbonate reabsorption/absolute sodium reabsorption was significantly higher in renal failure than in control. These data demonstrate that renal failure is associated with enhanced bicarbonate reabsorption which is not related to the state of extracellular volume, the need to increase acid excretion or the concentrations of parathyroid hormone. These findings suggest that there are additional unknown factors controlling bicarbonate reabsorption in renal failure. Reabsorption des bicarbonates dans l'insuffisance renale chronique. La reabsorption des bicarbonates a ete etudiee chez des chiens avant et apres la creation d'une insuffisance renale obtenue par l'infarcissement d'un rein et l'ablation du rein oppose. Le debit de filtration glomerulaire et le debit plasmatique renal atteignent respectivement 21 et 37% des valeurs temoins. Les excretions fractionnelles de potassium et de phosphate augmentent significativement. L'expansion du volume extra-cellulaire a pour consequence une diminution significative de la reabsorption des bicarbonates a la fois chez les animaux temoins et les uremiques. A un niveau comparable d'excretion fractionnelle du chlore, la reabsorption des bicarbonates est significativement plus grande chez les animaux uremiques que chez les temoins. Du bicarbonate de sodium a ete donne par voie orale a un second groupe de chiens, apres l'induction de l'insuffisance renale, a des doses suffisantes pour neutraliser la production endogene d'acide. La reabsorption des bicarbonates, la encore, est superieure a celle des temoins. La thyroparathyroidectomie ne modifie pas la reabsorption des bicarbonates. Les reabsorptions absolues de bicarbonate et de sodium sont lineairement correlees chez les temoins et au cours de l'insuffisance renale. Le rapport reabsorption absolue de bicarbonate/reabsorption absolue de sodium est significativement plus eleve dans l'insuffisance renale. Ces observations demontrent que l'insuffisance renale est associee a une augmentation de la reabsorption des bicarbonates qui n'est pas liee a l'etat du volume extra-cellulaire ou a la concentration d'hormone parathyroidienne. Ces constatations suggerent que des facteurs additionnels incorrus controlent la reabsorption des bicarbonates dans l'insuffisance renale.