Exaggerated carbohydrate-induced calciuria in the remaining kidney of transplant donors

Exaggerated carbohydrate-induced calciuria in the remaining kidney of transplant donors. Calcium excretion by the remaining kidney of transplant donors must double in order to maintain homeostasis, assuming that calcium accession from gut and bone is unaltered following unilateral nephrectomy. We have performed clearance studies on 12 donors and six normal subjects in order to characterize the pattern of calcium excretion by the remaining donor kidney as compared to normals, and to determine if an alteration in the calciuric response to carbohydrate ingestion occurs in this setting. Urinary calcium excretion in the remaining donor kidney exceeded that of one kidney in normals by approximately two-fold. Increased excretion was due to an increase in filtered load of calcium associated with an increase in fractional excretion. A similar increase in the rates of magnesium, phosphate, sodium and potassium excretion was also observed in donor kidneys. Following ingestion of 150 g of glucose, the maximum absolute increment in the rate of donor kidney calcium excretion was 108% greater than that observed in each kidney of normals. Also, there was an associated accentuation of the normal carbohydrate-induced effect upon magnesium and potassium excretion. Thus, the remaining kidney of transplant donors maintains homeostasis by doubling solute excretion. In addition, the observed exaggerated effect of carbohydrate ingestion on calcium as well as magnesium and potassium excretion is suggestive of altered metabolic activity within adapted nephrons of the remaining donor kidney. Calciurie exagérée, induite par les hydrates de carbone, du rein restant des donneurs. L'excrétion du calcium par le rein restant des donneurs doit doubler de façon à maintenir l'homéostasie, si l'on suppose que l'admission du calcium par l'intestin et l'os n'est pas modifiée par une néphrectomie unilatérale. Nous avons réalisé des études de clearances chez 12 donneurs et 6 sujets normaux de façon à: caractériser les modalités d'excrétion du calcium par le rein restant du donneur, comparé aux reins normaux; et à déterminer l'existence éventuelle d'une modification de la réponse aux hydrates de carbone dans cette situation. L'excrétion urinaire du calcium par le rein restant du donneur était approximativement le double de celle d'un rein normal. L'augmentation de l'excrétion était due à une augmentation de la charge de calcium filtrée associée à une augmentation de l'excrétion fractionnelle. Une