title: Assay of unfractionated and LMW heparin with chromogenic substrates: twin methods with factor Xa and thrombin.
abstract: Utilizing two newly synthesized chromogenic substrates (CS), two different assay methods for heparin in plasma have been developed. The assay with bovine factor Xa and the highly reactive "Substrate FXa-1" (CH3 OCO-D-CHA-Gly-Arg-pNA X AcOH) measures both unfractionated (UF) heparin and low molecular weight (LMW) heparin within a single standard curve in the 0.05-1.5 U/ml plasma range. The very similar (and less expensive) assay with bovine thrombin and "Substrate Th-1" (2AcOH X H-D-CHG-Ala-Arg-pNA), measures UF heparin, but not LMW heparin. The standard curves are highly reproducible (CV 3.5-4.7%). For clinical work, a linear standard curve is obtained with three standards and lin-log plot. The "within run" SD was 0.007-0.026 U/ml. Mean recovery of 0.5 U/ml heparin added to 10 pathological plasma samples ranged 0.46-0.53 U/ml (SD 0.034-0.040). Activities of three UF heparin and three LMW heparin preparations are reported.
mesh_terms: D000818:Animals; D002863:Chromogenic Compounds; D005170:Factor X; D006493:Heparin / Q000032:analysis*; D006801:Humans; D008722:Methods; D012016:Reference Values; D013552:Swine; D013917:Thrombin
chemical_list: D002863:Chromogenic Compounds; D005170:Factor X; D006493:Heparin; D013917:Thrombin