Comparison of dialysis programmes on different molecular prescriptions: a preliminary study.

Five dialysis and/or adsorbent therapy programmes were compared to examine the biological toxicity of both small and middle molecular fractions from the clinical viewpoint. With combination of various surface areas, diffusion pool sizes, or use of charcoal, what can be called a 'molecular prescription' is possible. The programmes were designed to bring about different degrees of removal of both fractions. Ultrafiltrates obtained with Amicon XM-10 hollow fibre filters before and after a programme were examined for levels of BUN, creatinine, and methylguanidine, inhibitory effect on pyruvate kinase, G-6-PDH, and LDH, and on the cell mortality rate of rat embryo liver cell monolayer culture. The worst results were obtained in those programmes which retained small molecular fractions and removed the middle molecular fractions efficiently. The biological toxicity of the small molecular fraction, from the viewpoint of maintaining the 'milieu intérieur', seems to be much stronger than that of the middle molecular fraction. A dialysis or adsorbent therapy programme removing the middle molecular fraction only, but leaving the small molecular fraction should be considered as putting the cart before the horse.