Screening of UV-absorbing solutes in uremic serum by reversed phase HPLC - change of blood levels in different therapies

In order to screen UV-absorbing solutes in large numbers of uremic serum samples, an automated liquid Chromatographic method was developed. The method proved to be reliable and reproducible in more than 500 analyses. HPLC separation was performed using gradient elution on a 25-cm Ultrasphere Octyl reversed phase column, with 5 jiim particles. Characteristic profiles for the uremic state were obtained in the analyses of serum samples of 43 uremic patients before and just after artificial kidney treatment; hemodialysis (n = 14), hemodiafiltration (n = 13) and hemofiltration (n = 16). In these profiles 20–40 peaks were resolved of which nine were ‘quantitated’ by peak height relative to a standard. Of these solutes creatinine, uracil, uric acid, hypoxanthine, indoxylsulfate, tryptophan and hippuric acid were identified. The heterogeneity of the population of uremic patients, with respect to the UV-absorbing solutes, was estimated. Significant differences of solute blood level changes during hemodialysis, hemodiafiltration and hemofiltration, were observed

Uremic toxins

It is the purpose of this paper to review our present knowledge about uremic toxicity, with a special emphasis on the methods that have been used to try to resolve this problem. More and more, sophisticated methods become available for the study of uremic toxicity. Many of these techniques are complicated and expensive, and have only a limited distinctive capacity. The HPLC method, however, is refined and allows a clear distinction between an impressive number of components. Moreover, there is a remarkable difference between the HPLC method appears to us as a valuable technique for the further study of uremic toxicity. At the moment, it is not possible to define each of the recognized products as uremic toxins. The aim should be, however, to eliminate retention products by dialysis in a way that the post-dialysis HPLC pattern resembles normal serum. Together with this strategy, the search for reliable markers of adequate dialysis should be continued

Uremic toxins

It is the purpose of this paper to review our present knowledge about uremic toxicity, with a special emphasis on the methods that have been used to try to resolve this problem. More and more, sophisticated methods become available for the study of uremic toxicity. Many of these techniques are complicated and expensive, and have only a limited distinctive capacity. The HPLC method, however, is refined and allows a clear distinction between an impressive number of components. Moreover, there is a remarkable difference between the HPLC method appears to us as a valuable technique for the further study of uremic toxicity. At the moment, it is not possible to define each of the recognized products as uremic toxins. The aim should be, however, to eliminate retention products by dialysis in a way that the post-dialysis HPLC pattern resembles normal serum. Together with this strategy, the search for reliable markers of adequate dialysis should be continued

Correlation of a colorimetric and a HPLC method for the determination of serum hippuric acid concentrations in uremia

Hippuric acid has been recognized as a potential marker of uremic toxicity in chronic renal failure. However, in most studies, serum hippuric acid concentrations have been determined by sophisticated methods, such as high-performance liquid chromatography. The present study was undertaken to evaluate whether the less complicated colorimetric determination method could replace such methods. Based on 21 different samples, the results obtained by both methods appeared to be correlated to each other in a highly significant way (total hippuric acid: r = 0.99, p less than 0.001; free hippuric acid; r = 1.00, p less than 0.001). Mean total and free hippuric acid concentrations and mean percent protein binding, obtained with both determination methods, were also identical. It is concluded that both the colorimetric method and high-performance liquid chromatography are equally reliable for the study of the concentration of hippuric acid in uremic serum and of its importance as a marker of the clinical and biochemical epiphenomena of uremic toxicity

Profiling of uremic serum by high-resolution gas chromatography-electron-impact, chemical ionization mass spectrometry

A fast and reliable procedure for gas chromatographic profiling of components in ultrafiltrated uremic serum has been developed, using glass capillary columns. Sample pretreatment consists of ultrafiltration, evaporation and silylation. Some twenty components are identified by electron-impact and chemical ionization mass spectrometry. A comparison is made between profiles of sera from a series of uremic patients, before and after hemodialysis, and from non-uremic sera. Significant differences are found between these profiles. A "dialysis ratio" is introduced as a parameter for the removal of retained components by hemodialysis treatment