In vitro cytotoxic properties of plasma samples from uremic patients.

The effect of uremic plasma on the growth of cultured cells was compared to that of control and of nonuremic plasma. Multiplication of D98 and 3T3 cells was measured by cell counting and by 3H-Thymidine incorporation. Uremic plasma was taken from severely uremic children (plasma creat. greater than 0.45 mM) and from hemodialyzed (HD) patients; plasma samples from HD patients were obtained at the beginning and the end of dialysis sessions. The 3H-Thymidine incorporation in the presence of uremic plasma (3665 +/- 520 cpm, n - 23) was lower than in the presence of control plasma (7700 +/- 1.080 cpm, n = 14) (P less than 0.01). The rate of 3H-Thymidine incorporation decreased regularly in the presence of increasing amounts of uremic plasma. 3H-Thymidine incorporation in post dialysis plasma was greater than in predialysis plasma (3902 +/- 664 cpm vs 9430 +/- 1540 cpm, n = 8) (P less than 0.01). To investigate the properties of the cytotoxic material, studies were performed with plasma ultrafiltrate (UF) and ultrafiltrate fractions obtained by G-15 Sepadex filtration. Uremic UF and fractions displayed no cytotoxic properties when cultured alone. Preincubation of uremic UF and the "middle molecular" fraction with control plasma restored a cytotoxic effect which, for total ultrafiltrate, was similar to that observed with uremic plasma. Thus, uremic plasma displays cytotoxic properties related to ultrafiltrable molecules which are not cytotoxic by themseleves but which are cytotoxic in the presence of plasma macromolecules.