The relationship between effluent potassium due to cellular release, free water transport and CA125 in peritoneal dialysis patients

Background. Recently, we found evidence of effluent potassium (K(+)) additional to diffusion and convection, suggesting cellular release (CR). Its relationship with free water transport (FWT) in stable peritoneal dialysis (PD) patients suggested an effect of hypertonicity of the dialysis solution leading to cell shrinkage. The aim of the present study was to reproduce these findings in groups according to PD duration and to further investigate the role of mesothelial cells in the observed phenomenon. Methods. Standard peritoneal permeability analyses done with 3.86% glucose were analysed cross-sectionally in three different groups: short-term (n = 53) 0–2 years PD treatment; medium-term (n = 24) 2–4 years PD and long-term (n = 26) > 4 years PD. Results. The time courses for FWT and cellular release of K(+) (CR-K(+)) during the dwell were not significantly different among the groups. Cancer antigen (CA) 125 was highest in the short-term group (P ≤ 0.02) and had a strong positive correlation with mass transfer area coefficient of creatinine (MTAC-creatinine) only in the short-term group (r = 0.62, P ≤ 0.01). CA125 had no relationship with either CR-K(+) or FWT, except for negative relationships in the short-term group (CR-K(+), r = −0.41, P ≤ 0.05; FWT, r = −0.54, P ≤ 0.05). Conclusion. We conclude that the correlation of CA125 and MTAC-creatinine is dependent on PD duration and underlines the in vitro observation that mesothelial cells produce vasoactive substances that may increase the peritoneal surface area. However, CA125 is not directly related to CR-K(+) or FWT. Therefore, the relationship between FWT and CR-K(+) is likely to reflect hypertonic cell shrinkage, regardless of the duration of PD, and confirms our earlier findings.