Growth factors in continuous ambulatory peritoneal dialysis effluent: their relation with peritoneal transport of small solutes

Abstract

Recent studies reveal conflicting results on the change of solute transfer with time on continuous ambulatory peritoneal dialysis (CAPD) and recurrent peritonitis. Herein, we performed a cross-sectional study of 76 patients on CAPD to examine their peritoneal permeability by measuring the dialysate to serum ratio of creatinine (D/P) and the mass transfer area coefficients of creatinine (MTACCr) or glucose (MTACGlu). Transforming growth factor-β1 (TGF-β1), platelet-derived growth factor (PDGF), and epidermal growth factor (EGF) were measured in the dialysate by ELISA. TGF-β1 mRNA in peritoneal macrophages were determined by a quantitative polymerase chain reaction. We failed to observe any correlation between the duration on dialysis and the peritoneal permeability in those patients with no previous peritonitis. Frequency of peritonitis episode did not affect the MTACCr, MTACGlu, or D/P. The MTACCr correlated well with MTACGlu (r = 0.78, p = 0.001) and with D/P (r = 0.98, p < 0.0001). No inverse correlation was demonstrated between dialysate PDGF or EGF and the peritoneal permeability. A positive correlation was demonstrated between the dialysate TGF-β1 and MTACCr, MTACGlu or D/P (r = 0.64, 0.54, and 0.64 respectively, p < 0.001). The dialysate TGF-β1 levels in patients with low D/P (≤ 0.5) were only half of that in patients with normal or high DIP (p = 0.0002). The dialysate levels of TGF-β1 did not correlate with PDGF or EGF. These findings raise the possibility that, other than diffusion across the peritoneal membrane from circulation, there could also be an intrinsic production of TGF-β1 by peritoneal cells in these CAPD patients. Our findings raise the speculation that TGF-β1 in dialysate from stable CAPD patients may exert an inhibitory action to fibroblast. Such action of TGF-β1 could reduce the risk of peritoneal sclerosis and hence, maintains a satisfactory peritoneal permeability to small solutes.