THE ROLE OF PLASMA COATING ON THE PERMEATION OF CYTOKINE-INDUCING SUBSTANCES THROUGH DIALYZER MEMBRANES

We studied the effects of coating of dialyser membranes with plasma pr oteins on the permeation of bacteria-derived cytokine-inducing substan ces (CIS). An in vitro dialysis circuit using polysulphone (PS) or mod ified cellulose triacetate (mCT) dialysers was used. Precoating of the dialysers was performed by recirculation of 10% normal human plasma f or 30 min in the blood compartment and subsequent rinse with pyrogen-f ree saline. Samples from the blood compartment were tested for inducti on of interleukin-1 alpha (IL-1 alpha), interleukin-1 beta (IL-1 beta) and tumour necrosis factor (TNF alpha) at various time points after c hallenging the dialysate with sterile culture supernatants from Pseudo monas aeruginosa. Contamination of the dialysate resulted in the appea rance of CIS in the blood compartment of both polysuphone modified cel lulose triacetate (IL-1 alpha: PS, time O: 81 +/- 11 pg/ml, time 60 mi n: 4747 +/- 1822 pg/ml, P < 0.05; mCT, time O: 235 +/- 141 pg/ml, time 60 min: 1632 +/- 531 pg/ml, P < 0.05). The plasma protein layer reduc ed the penetration of CIS significantly only for polysulphone (IL-1 al pha: PS, time 60: 4747 +/- 1822 versus 880 +/- 525 pg/ml, P < 0.05; mo dified cellulose triacetate, time 60 min: 1632 +/- 531 pg/ml versus 93 0 +/- 326 pg/ml). Samples from the blood compartment contained < 6 pg/ ml LAL-reactive material at all time points. We conclude that plasma c oating of polysulphone dialysers reduces the permeability for CIS deri ved from Pseudomonas, either by reducing the effective pore size or by adsorption of proteins that bind CIS. When precoated dialysers were u sed, transfer of CIS through both dialysers was comparable, suggesting that under the conditions of in vivo haemodialysis there may be no di fference between the dialysers regarding the penetration of CIS from t he dialysate.