Middle Molecules Re-Examined

Abstract

Evidence for and against the presence and pathophysiologic importance of middle molecules in uremia is reviewed. The evidence favors both their presence and importance.

Molecules in the Middle Molecular Weight Range

“…As soon as this hypothesis was formulated, and even before the presence of MM had been detected in biological fluids of uremic subjects, great improvements in dialysis techniques were made, due to the search for membranes with greater permeability to substances with a MW of 1.000-2,000 daltons [4,20,23,32,33,43], Dall'Aglio et al [17] showed the accumulation (in sera, urine and dialysis fluids) of components estimated to have a MW lower than 3,500 daltons in uremic patients, using various types of chromatography on Sephadex gels. Dzurik et al [18], without making reference to the MM hypothesis, also isolated, by chromatography of the sera of uremic patients, a toxin with a MW estimated at 1.000-1,500 daltons.…”