Inhibitory effects of plasma dialysate on protein synthesis in vitro: influence of dialysis and transplantation

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Abstract
An in vitro technique was designed to measure the protein synthesis rate in the presence of plasma dialysate from severely uremic patients. Some of them were treated with a poor nitrogen diet, hemodialysis, or transplantation. The data observed with plasma of such patients were compared to those obtained with plasma dialysate of control subjects. Each plasma sample was dialyzed for 24 hr to extract the molecules having molecular weights less than 12,000 and the dialysate was lyophilized. Protein synthesis was studied in vitro, using a cell-free system from mouse Krebs II ascites cells. The cells were lysed, and the 30,000 × g supernatant (“S-30 lysate”) was used to test the protein synthesizing activity of the plasma dialysate from control and uremic animals. The rate of protein synthesis was monitored by measuring the incorporation of a radiolabel (3H-leucine) into trichloroacetic acid-precipitable material in the presence of increasing amounts of plasma dialysate. In the presence of dialysate plasma from uremic patients as well as from hemodialyzed (HD) patients sampled before dialysis, there was a decrease in the 3H-leucine incorporation rate when the amount of added dialysate increased in the incubating medium. In severely uremic patients a difference between a high or low nitrogen diet could not be demonstrated. Though the count level of incorporated leucine with plasma from HD patients was always lower than that recorded in the presence of non-HD patients, the difference was not significant. However both these incorporation curves were significantly lower than the control curve (P < 0.01). Plasma specimens from HD patients were obtained at the beginning and end of a dialysis session. The comparison between the pre- and postdialysis incorporation curve showed an obvious improvement in the leucine incorporation rate with postdialysis plasma dialysate. In all transplanted patients but one, the incorporation curve was similar to the control curve. Therefore, it could be concluded 1) that uremic plasma inhibits protein synthesis, 2) predialysis plasma has the same inhibitory effect on in vitro protein synthesis as plasma from non-HD patients, 3) dialysis removes a great part of this inhibitory effect which appears to be related to dialyzable molecules, and 4) successful transplantation restores a normal pattern of in vitro protein synthesis.

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