COMPETITIVE SOLID-PHASE ENZYME-IMMUNOASSAY FOR MELATONIN IN HUMAN ANDRAT SERUM AND RAT PINEAL-GLAND

We describe a solid-phase competitive enzyme immunoassay for determina tion of melatonin in serum. The detection limit of the assay is 1.0 fm ol/well. Low cross-reactivity of the antiserum with other indoles, par allel serum extract dilution and melatonin standard curves, good analy tical recovery, and within- and between-assay CVs of 6.4-14.4% provide validation of the assay. Linear regression analysis of melatonin conc entrations measured with this assay (y) and with a commercial H-3 RIA (x) in 88 sera yielded the relation y = 0.62 x - 0.76, S(y\x) = 0.03. Values for melatonin in serum samples from healthy subjects are lower during the day than during the night. Melatonin response in rat serum and pineal gland to isoproterenol injection is similar to published RI A data. The analytical procedure is also simple. Thus, the assay shoul d have practical applications in investigation of pineal function in b oth clinical and basic studies.