In vitro cytotoxic properties of plasma fractions from uremic patients

The growth of cultured cells was studied in the presence of control and uremic plasma. Cell multiplication was observed by in situ countings and measured by 3H-thymidine incorporation during one population doubling time of mouse 3T3 fibroblasts. Uremic plasma were taken from severe uremic patients (plasma creat. greater than 0.45 mM/L) and from hemodialysed (HD) patients: plasma from HD patients were obtained at the beginning and end of a dialysis session. The 3H-Thymidine incorporation in the presence of uremic plasma was decreased (3620 +/- 160 cpm, n = 16) as compared to the control incorporation (8500 +/- 520 cpm, n = 14) (p 0.01). The comparison between the pre- and post-dialysis incorporation values (3900 +/- 660 cpm vs 9580 +/- 1600 cpm, n = 8) showed a significant increase of the 3H-Thymidine incorporation in the presence of post-dialysis plasma (paired t test: p less than 0.01) which did not differ from that of control plasma. To obtain information on the properties of the cytotoxic material, incubations were made with ultrafiltrate (UF) of plasma and UF middle molecular weight fraction of UF obtained by G-15 Sephadex filtration. Uremic UF and fraction displayed no cytotoxic properties when added alone to the culture medium. The pre-incubation of uremic UF and "middle molecule" fraction with control plasma restored a cytotoxic effect which was not different from that observed with total uremic plasma. Uremic plasma induces an inhibition of the growth of cultured cells. That is due to ultrafiltrate molecules abnormally accumulated in uremic plasma which are inhibitory when mixed with plasma macromolecules.