[Specific assay for endotoxin using immobilized histidine. Application to serum sample]

The amount of endotoxin in the serum was measured by the new assay method of endotoxin using a filtercup, Limulus amebocyte lysate, and immobilized histidine which is a specific adsorbent for endotoxin. The maximum recovery of endotoxin in the rabbit serum was obtained using acetate buffer (pH 5.5, mu = 0.1) for the adsorption. Using this buffer, various kinds of endotoxin in water were adsorbed quantitatively on immobilized histidine, and the activity of the adsorbed endotoxin was well recovered. The value of the amount of endotoxin in the bovine serum measured by the new assay method, which includes heat treatment (70 degrees C, 10 min) after separation followed by washing, was closer to that calculated from pyrogenic activities in rabbits than that measured by the PCA-Toxicolor method.