Calcemic and phosphaturic response to parathyroid hormone in normal and chronically uremic dogs

Calcemic and phosphaturic response to parathyroid hormone in normal and chronically uremic dogs. It is well established that the calcemic response to parathyroid hormone (PTH) is blunted in chronic uremia and is corrected partially by 1,25(OH) 2 D treatment. Recent evidence suggests that PTH(1-34) and not PTH(1-84) may be the actual calcemic fragment. Equivalent doses of both peptides were infused into five normal dogs (GFR = 51 ml/min) and eight dogs with a remnant kidney and chronic renal insufficiency (GFR = 15 ml/min). Both the calcemic and phosphaturic responses were studied. Remnant dogs had a blunted calcemic response to bPTH(1-84). The increase in fractional phosphate excretion was similar. In contrast, the calcemic response to bPTH(1-34) was equivalent in remnant and normal dogs. Treatment of uremic dogs with 400ng 1,25(OH) 2 D daily for 3 days restored the effect of bPTH(1-84) on serum calcium and increased the control value for tubular phosphate reabsorption from 28 ± 3 µg/ml GFR to 37 ± 4 µg/ml GFR (P 2 D may be involved in metabolism of PTH(1-84). In addition, the effect of PTH on fractional phosphate excretion is not magnified in nonparathyroidectomized uremic dogs. Reponses calcemiques et phosphaturiques a l'hormone parathyroidienne chez des chiens normaux et uremiques chroniques. Il est bien connu que la reponse calcemique a l'hormone parathyroidienne (PTH) est diminuee lors de l'uremie chronique, et est partiellement corrigee par un traitement avec de la 1,25(OH) 2 D. Des resultats recents suggerent que la PTH (1-34) et non la PTH (1-84), pourrait etre le veritable fragment hypercalcemiant. Des doses equivalentes des deux peptides etaient perfuse chez cinq chiens normaux (GFR = 51 ml/min) et chez huit chiens ayant un rein restant reduit, et une insuffisance renale chronique (GFR = 15 ml/min). Les reponses calcemiques et phosphaturiques etaient etudiees. Les chiens insuffisants renaux avaient une diminution de la reponse calcemique a la bPTH (1-84). L'augmentation de l'excretion fractionnelle des phosphates etait identique. Au contraire, la reponse calcemique a la bPTH (1-34) etait equivalente chez les chiens normaux et uremiques. Le traitement des chiens uremiques avec 400ng de 1,25(OH) 2 D chaque jour pendant 3 jours a restaure l'effet de la bPTH (1-84) sur la calcemie et a augmente la valeur controle de la reabsorption tubulaire des phosphates de 28 ± 3 µg/ml GFR a 37 ± 4 µg/ml GFR (P 2 D pourrait etre impliquee dans le metabolisme de la PTH (1-84). En outre, l'effet de la PTH sur l'excretion fractionnelle des phosphates n'est pas amplifie chez les chiens uremiques non parathyroidectomises.