CANCER ANTIGEN 125 IS LOCALLY PRODUCED IN THE PERITONEAL-CAVITY DURING CONTINUOUS AMBULATORY PERITONEAL-DIALYSIS

The local production of cancer antigen (CA) 125 in the peritoneal cavi ty of 14 continuous ambulatory peritoneal dialysis patients was studie d. In addition, the relationship between the concentration of mesothel ial cells and CA 125 in the peritoneal dialysate effluent was examined . The median results and ranges were as follows: plasma CA 125 14 U/mL (range 10 - 23), dialysate CA 125 18 U/mL (range 5.2 - 76), dialysate /plasma ratio 1.9 (range 0.61 - 5.4), and number of mesothelial cells 400/mL (range 10 - 5000). Peritoneal concentrations of mesothelial cel ls and CA 125 were positively correlated (r = 0.50, p < 0.01). Using a monoclonal antibody, CA 125-positive cells were found in the cytospin preparations of the cells of dialysis effluents. All these CA 125 pos itive cells were also positive for cytokeratin used as a mesothelial c ell marker. In vitro experiments using mesothelial cells in monolayers showed a linear increase in CA 125 concentration both in time and in relation to the number of mesothelial cells. From these experiments a production rate of 24 U/hour/10(6) cells could be calculated. It is th erefore concluded that CA 125 is locally produced in the peritoneal ca vity during CAPD and that the mesothelial cells are the major source o f this CA 125.