title: Radioimmunoassay of serotonin (5-hydroxytryptamine) in cerebrospinal fluid, plasma, and serum.
abstract: We describe a direct radioimmunoassay for serotonin (5-hydroxytryptamine) in cerebrospinal fluid, platelet-poor plasma, and serum. We raised antisera in rabbits against serotonin diazotized to a conjugate of bovine albumin and D,L-p-aminophenylalanine. Polyethylene glycol, alone or in combination with anti-rabbit immunoglobulins, is used to separate bound and unbound tritiated serotonin. The minimum concentration of serotonin detectable is 2 nmol/L in a 200-microL sample. Within-day precision (CV) is 4.3%, between-day precision 7.7%. Analytical recoveries of serotonin are 109% and 101% for cerebrospinal fluid and plasma, respectively. Tryptophan, 5-hydroxytryptophan, 5-hydroxyindoleacetic acid, and 5-hydroxytryptophol do not interfere with the assay. However, 5-methoxytryptamine and tryptamine cross react. Of samples of cerebrospinal fluid from patients with disc herniations (n = 21) or low-pressure hydrocephalus (n = 10), one-third had concentrations of 2-4 nmol/L and two-thirds were below the minimum detectable concentration. The observed range for the concentration of serotonin in plasma of 14 normal subjects was 5-14 nmol/L (mean +/- SD, 9 +/- 3 nmol/L). The observed ranges for serotonin in serum were: for 10 women 520-900 (mean +/- SD: 695 +/- 110) nmol/L and for 10 men 380-680 (520 +/- 94) nmol/L.
mesh_terms: D000328:Adult; D000917:Antibody Formation; D003429:Cross Reactions; D005260:Female; D006801:Humans; D006849:Hydrocephalus / Q000097:blood / Q000134:cerebrospinal fluid; D007405:Intervertebral Disc Displacement / Q000097:blood / Q000134:cerebrospinal fluid; D008297:Male; D008875:Middle Aged; D011863:Radioimmunoassay; D012016:Reference Values; D012701:Serotonin / Q000097:blood / Q000134:cerebrospinal fluid* / Q000276:immunology
chemical_list: D012701:Serotonin