Distribution of antithrombin III and glucosylceramide in human plasma lipoproteins and lipoprotein deficient plasma.

We have investigated the distribution of antithrombin-III and glucosylceramide (Glc-Cer) in human plasma, plasma lipoproteins and lipoprotein-deficient plasma. Antithrombin III activity was measured employing immunochemical and biological assays. Glc-Cer was quantified by gas liquid chromatography (GLC). Whole plasma contained 145 micrograms antithrombin III/ml plasma, all of which was associated with the lipoprotein-deficient plasma (d greater than 1.25 g/ml). Whereas, most if not all the plasma GlcCer was associated with plasma low density lipoproteins (LDL) (d-1.022-1.055 g/ml) and high density lipoproteins (HDL) (d-1.063-1.25). GlcCer was not found in the lipoprotein-deficient plasma. We conclude that GlcCer on lipoproteins does not contribute to antithrombin III activity. Moreover, the absence of GlcCer in lipoprotein-deficient plasma does not impair antithrombin-III activity.