Abstract: Objective  To study the effect of calcium ion concentration in peritoneal dialysate on peritoneal fibrosis, epithelial mesenchymal transition (EMT) and endoplasmic reticulum stress (ERS) of peritoneal dialysis patients.  Method   A randomized controlled study was conducted on patients who underwent continuous non-bedridden peritoneal dialysis using standard calcium peritoneal dialysate. They were divided into low calcium group and control group. Patients in low calcium group switched to low calcium peritoneal dialysate while those in the control group continued to use the peritoneal dialysate with standard calcium concentration. The enrollment time point was set at 0 month and the end of the experiment was set after 6 months. Their clinical data at the time of enrollment were recorded. The outflow dialysates at 0 and 6 months were collected to measure the contents of transforming growth factors-β1 (TGF-β1), fibronectin (FN) and collagen-I (Col-I), and the expression levels of E-cadherin, N-cadherin, ZO-1, α-smooth muscle actin (α-SMA), CCAAT enhancer binding protein homologous protein (CHOP), phosphorylated protein kinase R-like endoplasmic reticulum kinase (p-PERK), phosphorylated eukaryotic translation initiation factor 2 α (p-eIF2α) and transcription activating factor 4 (ATF4).  Results  A total of 49 patients were enrolled, including 24 in low calcium group and 25 in control group. After 6 months of treatment, the contents of TGF-β1, FN, Col-I and the expression levels of α-SMA, N-cadherin, p-PERK, p-eIF2α, ATF4 and CHOP were lower in low calcium group than in control group  (t=4.599, 2.161, 6.557, 9.357, 8.565, 8.634, 7.518, 8.842 and 10.989 respectively; P＜0.001, =0.036, ＜0.001, ＜0.001, ＜0.001, ＜0.001, ＜0.001, ＜0.001 and ＜0.001 respectively), while the expression levels of E-cadherin and ZO-1were higher in low calcium group than in control group (t=16.684 and 22.273; P＜0.001 and＜0.001).  Conclusion  Low calcium dialysate can alleviate peritoneal fibrosis, of which the molecular mechanism may relate to the inhibition of EMT and ERS by low calcium dialysate.

Key words: Peritoneal dialysis, Low calcium dialysate, Peritoneal fibrosis, Epithelial interstitial transformation, Endoplasmic reticulum stress