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Reabsorption of lithium and phosphate by the rat kidney: Role of the parathyroids

1974; Elsevier BV; Volume: 5; Issue: 3 Linguagem: Inglês

10.1038/ki.1974.24

1523-1755

Thomas H. Steele, Kathryn L. Dudgeon,

Pharmacological Effects and Toxicity Studies

Reabsorption of lithium and phosphate by the rat kidney: Role of the parathyroids. Because of the possibility that lithium reabsorption may parallel proximal tubular reabsorption in general, the fractional excretions of lithium (FELi), phosphate (FEP) and sodium (FENa) were compared in rats preloaded intraperitoneally with lithium during hydropenia and during stepwise NaCl/HCO3 volume expansion at 150 and 600 µl/min. In intact rats, all three indexes increased significantly during volume expansion. After acute parathyroidectomy, FEP values during hydropenia were 93% less than in the intact animals. Again, FELi, FEP and FENa all increased significantly during progressive volume expansion, but the increase in FEP was less than 1% of the increase in the intact rats. When chronically parathyroidectomized rats were studied, FELi and FENa again increased during volume expansion. However, FEP values did not increase, but remained at very low levels similar to those in the acutely parathyroidectomized animals. Calcium and magnesium infusion, separately and together, in other acutely parathyroidectomized volume-expanded rats did not decrease FELi. The results indicate that lithium reabsorption in the rat is not affected by the functional status of the parathyroid glands or the presence of parathyroid hormone. Parathyroidectomy dissociates changes in lithium and phosphate reabsorption during volume expansion. Reabsorption du lithium et du phosphate par le rein de rat: Role parathyroides. En fonction de la possibilite que la reabsorption du lithium puisse etre parallele a la reabsorption proximale en general, les excretions fractionnelles du lithium (FELi), de phosphate (FEP) et du sodium (FENa) ont ete comparees, chez des rats prealablement charges en lithium par voie intra-peritoneale, au cours de l'hydropenie et durant une expansion progressive par NaCl/HCO3 a 150 et 600 µl/min. Chez les rats normaux les trois valeurs augmentent significativement durant l'expansion. Apres parathyroidectomie aigue les valeurs de FEP en hydropenie sont inferieures de 93% a celles des animaux intacts. FELi, FEP et FENa ont augmente significativement durant l'expansion, mais l'augmentation est de moins de 1% de celle des rats intacts. Chez des rats parathyroidectomises chroniques FELi et FENa augmentent pendant l'expansion mais FEP n'augmente pas, sa valeur reste tres basse, semblable a celle des animaux parathyroidectomises aigus. Des infusions de calcium et de magnesium, simultanees ou separees, n'ont pas diminue FELi chez d'autres animaux parathyroidectomises aigus soumis a l'expansion. Les resultats indiquent que la reabsorption du lithium chez le rat n'est pas affectee par l'etat fonctionnel des glandes parathyroids ou la presence d'hormone parathyroidienne. La parathyroidectomie dissocie les modifications des reabsorptions du lithium et du phosphate au cours de l'expansion.