Changes in peritoneal membrane permeability and proteinuria in patients on peritoneal dialysis after treatment with paricalcitol - a preliminary study

Background: Patients on peritoneal dialysis (PD) have protein loss through peritoneal membrane (PM) and experience changes in permeability of the membrane. Paricalcitol is a selective vitamin D receptor activator with an effect upon systemic inflammation and an inhibitory effect upon the renin-angiotensin-aldosterone system (RAAS). Methods: This study explores the possible effect of paricalcitol upon the PM in 23 patients on PD with high iPTH levels. Peritoneal kinetic studies were performed before and after paricalcitol, measuring also ultrafiltration/day, peritoneal protein losses and proteinuria. Results were compared with a control group of 15 patients not receiving any form of vitamin D. Results: With a mean dose of 1.3 mu g/day, peritoneal protein loss decreased from 0.91 +/- 0.35 to 0.76 +/- 0.26 g/l (15.4%) (p = 0.007) and from 7.55 to 6.46 g/d (p < 0.033), and ultrafiltration increased from 844 to 1,002 ml/d (15.8%) (p = 0.037) and from 284 to 323 ml/4 h. (NS), with minimal change in the creatinine dialysate/plasma ratio 0.67 +/- 0.12 vs. 0.65 +/- 0.11. Proteinuria decreased from 1.65 to 1.25 g/l (21.9%) (p = 0.01) and iPTH decreased from 668 +/- 303 to 291 +/- 148 pg/ml (p < 0.001). In the control group, no changes in peritoneal membrane permeability and proteinuria were found. Conclusions: The results of the study indicate that paricalcitol is effective in treating hyperparathyroidism in patients on PD, and suggest an effect upon proteinuria and PM permeability (not previously reported), with diminished peritoneal protein loss and increased ultrafiltration. The antiinflammatory, antifibrotic and RAAS-modulating actions described for paricalcitol may be responsible for these findings, and could be important for preserving the peritoneum as a dialyzing membrane.