Renal calcium handling after rapamycin conversion in chronic allograft dysfunction

To study the effect of rapamycin on calcium balance, we conducted a prospective study on transplant recipients. The patients were converted to rapamycin and observed for 6 months (C). Urinary Ca and P, ALK-p, Ca, P, and intact parathyroid hormone (iPTH) were examined before and 6 months after conversion. A nonconversion group (N) was found for comparison. Sixteen patients entered the study. There were increases of ALK-p (C: 67.4 ± 32.9 to 79.6 ± 37.0*; N: 67.3 ± 25.1 to 67.8 ± 14.7 IU) (*P < 0.05), Ca²⁺ (C: 8.7 ± 0.3 to 9.5 ± 0.2*; N: 8.8 ± 0.4 to 8.7 ± 0.5 mg/dl), urinary P excretion (C: 287.6 ± 257.1 to 439.4 ± 260.9*; N: 233.9 ± 117.2 to 264.8 ± 143.4 mg/day) and iPTH (C: 133.7 ± 149.6 to 200.6 ± 171.5*; N: 128.4 ± 57.1 to 136.3 ± 40.4 pg/ml). Serum P (C: 5.3 ± 1.4 to 3.6 ± 0.6*; N: 5.2 ± 0.8 to 5.1 ± 0.9 mg/dl) and urinary Ca²⁺ (C: 93.9 ± 52.6 to 31.8 ± 45.1*; N: 84.6 ± 38.3 to 75.9 ± 38.4 mg/day) were decrease. Rapamycin was associated with decreased urinary Ca²⁺ and increased P excretion. The alteration might come from the increased parathyroid hormone.