Better preservation of peritoneal morphologic features and defense in ratsafter long-term exposure to a bicarbonate/lactate-buffered solution

The Ion-term effects of a standard lactate-buffered dialysis fluid and a ne w, two-chamber, bicarbonate/lactate-buffered dialysis fluid (with fewer glu cose degradation products and a neutral pH) were compared in an in vivo per itoneal exposure model. Rats were given daily injections, via an access por t, of 10 ml of standard solution or bicarbonate/lactate-buffered solution f or 9 to 10 wk. The omentum, peritoneum, and mesothelial cell layer were scr eened for morphologic changes. In addition, the bacterial clearing capacity of the peritoneal cells was studied. Significantly more milky spots and bl ood vessels were observed in the omenta of animals treated with standard so lution (P < 0.03 for both parameters). Electron-microscopic analysis demons trated dramatic changes in the appearance of the vascular endothelial cells of the milky spots and a severely damaged or even absent mesothelium on th e peritoneal membrane of the standard solution-treated animals. In contrast , the mesothelium was still present in the bicarbonate/lactate-buffered sol ution group, although the cells lost microvilli. Both peritoneal dialysis f luids significantly increased the density of mesothelial cells (per square millimeter) on the surface of the liver and the thickness of the submesothe lial extracellular matrix of the peritoneum (both P < 0.04 for both fluids versus control). A significantly better ex vivo bacterial clearing capacity was observed with peritoneal cells from the bicarbonate/lactate-buffered s olution group, compared with the standard solution group (P < 0.05 in both experiments). These results demonstrate that instillation of bicarbonate/la ctate-buffered solution into rats for 9 to 10 wk preserves both morphologic and immune parameters much more effectively, compared with standard soluti on. These findings may be of considerable clinical importance.