AN ENZYME-IMMUNOASSAY FOR 6-SULPHATOXY-MELATONIN IN HUMAN URINE

We describe a newly developed enzyme immunoassay (EIA) for the determi nation of 6-sulphatoxy-melatonin (aMT6s) in human urine, using a aMT6s -bovine serum albumin-horseradish peroxidase (aMT6s-BSA-HRP) conjugate as the enzyme label, The assay incorporates a highly specific antibod y raised in rabbits. The EIA has a sensitivity of 2 pg/well (40 pg/ml) with intraassay coefficients of variation of 2.3-6.1% in the range of the assay. The material with the highest level of cross-reactivity wa s N-acetyl serotonin sulphate, with a relative potency of 0.000078%. O ne hundred thirty-four urine samples from children and adults at diffe rent time points were assayed and the results compared with those from an established radioimmunoassay (RIA) and with a newly developed RIA using the same antibody as the EIA. The correlation coefficient, r; co mparing the two RIA's was 0.9869, and the regression equation was log (kit) = 0.9340 log (new) + 0.1213. The correlation coefficient, I; com paring the EIA with the newly developed RIA, was 0.9686, and regressio n equation log (new) = 0.9674 log (EIA) + 0.0600. The EIA for the meas urement of aMT6s in urine represents a new approach in the investigati on of pineal function.