A simplified radioimmunoassay for melatonin and its application to biological fluids. Preliminary observations on the half-life of plasma melatonin in man.
A simplified and rapid radioimmunoassay (RIA) for melatonin is presented. Melatonin is extracted from seru, plasma or urine and RIA is performed by using [3H]melatonin as the tracer. The standard curve covers the range 0.2--4.3 nmol/l. By increasing the sample volume the range can be extended to 0.06 nmol/l. The intra-assay variability is 7% (relative standard deviation = rsd) and the inter-assay variability is 10% (rsd). The recovery of melatonin added to calf serum is 96%. The long term variability of the assay (43 assays on aliquots of one serum sample during 6 months) is 13.5% (rsd). The serum levels in man after one oral dose of 430 mumol melatonin have been measured. The peak value, 620 nmol/l, was noted after 0.5 h and the melatonin concentration was still above the normal range at 24 h (2.1 nmol/l).
D013006:Growth Hormone / Q000097:blood; D006207:Half-Life; D006801:Humans; D007700:Kinetics; D008550:Melatonin / Q000032:analysis* / Q000097:blood / Q000494:pharmacology; D008657:Metabolic Clearance Rate; D011863:Radioimmunoassay / Q000379:methods; D013002:Somatomedins / Q000097:blood
D013002:Somatomedins; D013006:Growth Hormone; D008550:Melatonin