Abstract
To clarify the factors that influence markers which reflect peritoneal function, the effect of peritoneal dialysis (PD) effluent and the medium calcium (Ca) level on cell injury and function was evaluated in cultured human peritoneal mesothelial cells (MCs) and fibroblasts (FBs). PD effluents were sampled with the peritoneal function test (PET) in 11 stable PD patients. To evaluate the effect of PD effluent on cell injury and function, confluent MCs and FBs were incubated with PD effluent, and LDH activities and concentrations of interleukin-6 (IL-6) and hyaluronic acid (HA) in the supernatants of the media were measured as markers of cell injury and cell function, respectively.
No significant difference was found in MC or FB derived LDH activities between the supernatants of media incubated with PD effluent and the control (F-12 medium). Although PD effluent did not cause any change in IL-6 or HA production by MC, it only significantly stimulated the IL-6 production by FB. By subculturing MC 2-4 times, MC proliferation and IL-6 production by MC per area were decreased according to the numbers of subculture.
Although the IL-6 production by MC, injured by incubation with new PD dialysate, was decreased, it was markedly increased at the incubation period of recovering from cell injury. At the 24 h-incubation of MC with various Ca (0.7-4.0mEq/l) levels in the media, a negative correlation was detected between the Ca levels and IL-6 concentrations in the supernatants (r=-0.928, p<0.0001), a positive correlation was found between the Ca levels in the media and the degree of MC injury (r=0, 854, p<0.0002), and a negative correlation was revealed between the degree of MC injury and IL-6 concentrations in the supernatants (r=-0.807, p<0.0006). Furthermore, elevation of the intracellular Ca level of MC induced by thapsigargin also caused an increase in the supernatant IL-6 concentrations.
These results indicate that PD effluent does not cause cell injury in MCs or FBs, but the PD effluent may accelerate IL-6 production by FB. The aging of MC induces the decrease in IL-6 production and the increase in cell surface area. When MC is injured by new PD fluid, IL-6 production is decreased, but the ability of IL-6 production is recovered accompanied by the healing of cell injury. The findings suggested that the Ca level in the culture medium is a regulatory factor of MC injury and IL-6 production by MCs.
