CHROMATOGRAPHIC TECHNIQUES AND BIDIRECTIONAL-DIFFUSION CELL IN THE SEPARATION AND CHARACTERIZATION OF UREMIC MIDDLE MOLECULES

ZINDOGA TIZ BUNGU, Purdue University

Abstract

In uremia there is a continual increase in the blood concentration of substances that may be toxic. Some of these uremic substances have been hypothesized as "middle molecules" (substances with molecular weight between 300 and 5,000 daltons). But characterization of the uremic "middle molecules" has been controversial. Three different groups of specimens were used in this investigation: serum from human hemodialysis patients, peritoneal fluid from continuous ambulatory peritoneal dialysis patients and serum from canine hemodialysis patients. In each case the specimens were subjected to dialysis in a bidirectional-diffusion cell and subsequent high performance liquid chromatography (anion exchange reverse phase size exclusion). The dialysances for the resultant peaks were calculated. In one experiment the specimens were digested by trypsin and analyzed also by high performance liquid chromatography. The results indicated that most of the substances in the peaks were small (< 300 daltons), many of the uremic substances dialyze as if they were protein bound, some of the uremic substances were peptides, most of the uremic substances were anionic, and the Sorbent Suspension Reciprocating Dialyzer was as effective as the Travenol Hollow Fiber Dialyzer in removing the uremic substances. It is concluded on the basis of the above results that uremic "middle molecules" may be small protein bound substances, and many of the uremic substances are anions. On these premises, it may be necessary to redefine the "Middle Molecule" hypothesis.

Degree

Ph.D.

Subject Area

Physiology

COinS