title: Serum serotonin levels determine the magnitude and type of bystander effects in medium transfer experiments.
abstract: Serotonin has been shown to be involved in the production of bystander signals by irradiated cells. In this study we examined the levels of serotonin in 10 different batches of commercially available fetal calf serum and correlated the serotonin levels with the toxicity of medium harvested from irradiated cells (ICCM) using a standard medium transfer colony-forming assay. The serotonin levels in the serum varied widely between batches, and the levels correlated directly with the toxicity of the harvested ICCM. Three serum samples had levels of serotonin below 25 ng/ml, and these did not show medium transfer bystander effects. Exposure of serum samples to normal daylight reduced serotonin levels significantly. We suggest that serum batch variability may underlie much of the observed interlaboratory variation in the ability to produce bystander effects and further suggest that serum batches should be protected from light and prescreened for their ability to produce a bystander effect using a positive control cell line.
authors.affiliation: Medical Physics and Applied Radiation Science Centre, McMaster University, Hamilton, Ontario, Canada, L8S 4K1. mothers@mcmaster.ca
authors.forename: Carmel
authors.initials: C
authors.lastname: Mothersill
authors.forename: Rohin
authors.initials: R
authors.lastname: Saroya
authors.forename: Richard W
authors.initials: RW
authors.lastname: Smith
authors.forename: Harleen
authors.initials: H
authors.lastname: Singh
authors.forename: Colin B
authors.initials: CB
authors.lastname: Seymour
mesh_terms: D000818:Animals; D024201:Bystander Effect; D002417:Cattle; D003470:Culture Media; D004797:Enzyme-Linked Immunosorbent Assay; D012701:Serotonin / Q000097:blood*
chemical_list: D003470:Culture Media; D012701:Serotonin