ENZYME IMMUNOASSAY FOR MEASUREMENT OF THE α SUBUNIT OF S100 PROTEIN IN HUMAN BIOLOGICAL FLUIDS

抄録

A sandwich-type immunoassay method for measurement of the α subunit of S100 protein in human biological fluids was developed by use of affinity-purified antibodies raised in rabbits with human S100a₀ (αα form ofS100 protein) as immunogen. The assay system consisted of polystyrene balls with immobilized antibody F(ab')₂ fragments and the same antibody Fab’ fragments labeled with β-D-galactosidase from Escherichia coli. The minimum detection limit of the assay was 3 pg S100a₀ per assay tube. The assay cross-reacted about 20% with S100a (αβ form of S100 protein), which contain an α subunit in the molecule, but showed no cross-reactivity with S100b (ββ form of S100 protein), indicating that the assay was specific to the α subunit of S100 protein (S100-α). Coefficients of variation in within-run and between-run precision studies for serum and urine S100-α were <15%. Concentrations of serum S100-α in healthy adults ranged from <0.060—0.464 ng/ml, and were significantly higher in male than in female. Concentrations in urine S100-α in normal adults ranged from 0.033 to 0.623 ng/ml showing no significant difference between the both sexes. Parotid saliva also contained a relatively high level (average value of 0.411 ng/ml) of S100-α, which was probably derived from serous acini of parotid gland. A preliminary determination of S100-α in urine samples from patients with kidney diseases showed that the S100-α concentrations were enhanced in some patients with renal cell carcinoma, nephritis and nephrosis.