title: Analysis of the cytotoxic effects of light-exposed HEPES-containing culture medium.
abstract: The addition of N-2-hydroxyethylpiperazine-N'-2-ethanesulfonic acid (HEPES) to RPMI 1640 medium markedly increases the production of cytotoxic products during exposure of the medium to visible light. The cytotoxicity has been analyzed by measuring uptake of [3H]thymidine by murine thymocytes cultured in preirradiated medium containing 25 mM HEPES. Complete inhibition of thymidine uptake was produced by exposing 50% of the culture medium to light for 3 h before addition of cells. The HEPES-mediated effect requires only that HEPES and riboflavin be exposed to light; other medium constituents are not necessary. Hydrogen peroxide is a principal cytotoxic agent produced in this system. It is demonstrated that most, but not all, of the inhibition of thymidine uptake can be attributed to hydrogen peroxide.
mesh_terms: D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D002460:Cell Line; D002470:Cell Survival / Q000187:drug effects / Q000528:radiation effects; D003470:Culture Media; D004307:Dose-Response Relationship, Radiation; D006531:HEPES; D006861:Hydrogen Peroxide / Q000494:pharmacology; D066298:In Vitro Techniques; D008027:Light; D051379:Mice; D010787:Photosensitivity Disorders; D010879:Piperazines; D013950:Thymus Gland / Q000187:drug effects / Q000528:radiation effects*; D013997:Time Factors; D014815:Vitamins / Q000494:pharmacology
chemical_list: D000975:Antioxidants; D003470:Culture Media; D010879:Piperazines; D014815:Vitamins; D006861:Hydrogen Peroxide; D006531:HEPES