Simple enzyme immunoassay for the measurement of immunoreactive chromogranin A in human plasma, urine and saliva

A simple and sensitive enzyme immunoassay (EIA) was developed for determini ng human chromogranin A (CgA) -like immunoreactivity (IR) with use of synth etic human CgA (344-374) as antigen. In the development of the present EIA system, purposely designed N-alpha biotinylated glycylglycyl-human CgA (344 -374), which was synthesized, was proved to be a useful biotinylated deriva tive. Typical standard curves ranged from 13.7 fmol/ml to 10 pmol/ml of CgA -like IR. In the present EIA, the curves for dilution of human plasma, urin e, and saliva paralleled the standard curve for synthetic human CgA (344-37 4). The intraassay coefficient of variation for measurement of human plasma CgA was from 2.6 to; to 8.5%. indicating that reliable determinations can be performed for human plasma. The levels of CgA-like IR were 0.34+/-0.08 p mol/ml (mean +/- SD, n = 10) in fasting normal plasma, 0.18+/-0.05 pmol/ml (n = 8) in urine, and 0.11+/-0.05 pmol /mL (n = 8) in saliva in the morning are comparable with the respective values in RIA reported in the previous papers.