IMPROVED FLUOROMETRIC ENZYMATIC SORBITOL ASSAY IN HUMAN BLOOD

Samples for use in the fluorometric enzymatic assay of sorbitol in ery throcytes are normally prepared using HClO4 and K2CO3. We have replace d these reagents with NaOH and ZnSO4. Human whole blood, erythrocyte a nd plasma samples prepared with NaOH and ZnSO4 are colorless and clear , while erythrocyte samples prepared with HClO4 and K2CO3 are a pale y ellow-brown color. The sorbitol dehydrogenase reaction in the supernat ant of the mixture of NaOH and ZnSO4 is inhibited, but ethylenediamine tetraacetate completely eliminates this effect. The sorbitol assay in erythrocytes prepared with NaOH and ZnSO4 shows higher sensitivity and reproducibility than did that with HClO4 and K2CO3. Recovery of sorbi tol added to erythrocytes is similar in both assay methods. Concentrat ions of whole blood and erythrocyte sorbitol assayed by the present me thod are significantly higher in diabetics than in normals. Poorly con trolled diabetics had higher whole blood and erythrocyte sorbitol than well-controlled diabetics. Whole blood sorbitol concentrations differ ed more between diabetic and normal subjects than did erythrocyte sorb itol concentrations. (C) 1998 Elsevier Science B.V. All rights reserve d.