Glykosylierte Hämoglobine - Bildung und Beseitigung der Aldiminform

Abstract

The first intermediate of the glycosylated hemoglobin is a labile aldimine compound (Schiff' Base), the amount of which is dependent on the concentration of hemoglobin andglucose. Consequently the formation of the stable ketoamine compound is mainly influenced by the level of the intermediate aldimine.From the comparison of the molar ratios it becomes evident that there is an excess of amino groups over the free aldehyde groups of the glucose. The amino group must be in its basic form (nucleophilic reagent) to react with the aldehyde group of the glucose. Therefore, the reactivity of the different amino groups depends on their individual pK. The Chromatographie and electrophoretic methods cannot differentiate between the aldimine and the ketoamine form of the adduct. Therefore, the aldimine should be eliminated before the determination of the glycosylated hemoglobin. This can be performed by repeated washing of the erythrocytes, by dialysis, by pH-shift or by chemical elimination. The chemical elimination of the Schiff base is performed by "transschiffization"-reaction with semicarbazide. The electrophoretic and Chromatographie behaviour of the stable ketoamine form ist not influenced by the eliminator reagent.

Bicentric evaluation of a teaching and treatment programme for Type 1 (insulin-dependent) diabetic patients: improvement of metabolic control and other measures of diabetes care for up to 22 months

“…Glycosylated haemoglobin: during 198l, in Vienna, the microcolumn method (Iso-Lab, [9]) was used (normal range 5.9%-8.7% of total haemoglobin, mean+2SD of a00normal controls). After a period of several weeks during which both methods were used in parallel, in January 1982 the analytical procedure was changed to the microcolumn method plus initial aldimine extraction of the Schiff base [10]. As a consequence, the normal range dropped to 4.9%-8.1% (mean+__ 2 SD of 50 normal controls).…”

Evaluierung eines neuen vollmechanisierten HPLC-lonenaustausch-Systems (Merck-Hitachi L-9100) zur Bestimmung der glykierten Hämoglobine

“…Das Merck/Hitachi-System läßt hier alle Optionen offen. Ein Aldimin-Eliminationsschritt kann der Analyse wie bei anderen Systemen vorgeschaltet werden [12]. Ist dieses nicht gewünscht, so kann das Merck/Hitachi-System eine labile HbA 1c -Fraktion ausweisen, unterscheidet in diesem Falle dann zwischen einem Wert für das stabile HbA 1c und einem rechnerischen "Totalem HbA 1c ".…”