[The functional characteristics of the calcium-regulating systems and the calcium content of the blood following a cadaveric kidney allograft].

Total plasma calcium (Ca), Ca renal reabsorption, Ca tissue transport, parathyroid hormones and calcitonin were measured in fasting 30 recipients of a renal allotransplant, 95 healthy subjects, 9 primary hyperparathyroidism patients, 12 patients with bronchial asthma and exogenic hypercorticism. Total Ca proved normal in 26 but lowered in 4 recipients. Canalicular Ca reabsorption got enhanced in 17 recipients with high parathormone levels in 10 of them. Normal Ca reabsorption was registered in 13 recipients through parathormone elevated in 6 of them. Tissue Ca binding enhanced in its high reabsorption in the transplant. The binding did not depend either on parathormone secretion intensity or cyclosporin A treatment, being partially determined by steroid therapy. When investigated under Ca intravenous drop infusion in 20 recipients and 14 healthy subjects, Ca tissue binding confirmed its physiochemical nature and revealed in one third of the recipients impaired buffer capacity of the tissues as well as Ca retention and release rates. The impairment was related neither to changes in the basal level nor with secretion fluctuations of parathormone and calcitonin. Increased tissue Ca binding accounts for the absence of hypercalcemia in renal transplantation.