title: Decreased 3H-uridine incorporation and increased 3H-adenosine incorporation by HeLa cells exposed to autologous culture fluid.
abstract: Actively growing HeLa monolayer cultures briefly exposed to the culture fluids (CF) from confluent HeLa cultures and labeled simultaneously or subsequently, incorporated less 3H-uridine (3H-UR) but more 3H-adenosine (3H-AR) than control cultures similarly exposed to fresh medium and labeled. Exposure to CF inhibited the uptake as well as the incorporation of 3H-UR by cultures. The inhibition of 3H-UR incorporation by CF-exposed cultures could be reduced by increasing the concentration of 3H-UR in the labeling medium. Both the inhibition of 3H-UR incorporation and the stimulation of 3H-AR incorporation were prevented by washing the CF-treated cultures with phosphate buffered saline before labeling. Similarly, both effects could be producted in HeLa cultures exposed to fresh medium containing 1 X 10(-5) M uridine instead of to CF. Therefore, the observed effects of CF on label incorporation were probably due to the presence of uridine or a related compound, and the inhibition of 3H-UR incorporation resulted from reduced uptake of 3H-UR rather than from reduced RNA synthesis by exposed cells. The active agent in the CF, formed only when cultures were incubated at physiological temperatures, was not a product of medium decay. It was a cellular product formed equally well by cultures incubated in medium containing dialysed or whole serum.
mesh_terms: D000241:Adenosine / Q000378:metabolism*; D001769:Blood; D003470:Culture Media; D006367:HeLa Cells; D012313:RNA / Q000096:biosynthesis; D014316:Tritium; D014529:Uridine / Q000378:metabolism*
chemical_list: D003470:Culture Media; D014316:Tritium; D012313:RNA; D000241:Adenosine; D014529:Uridine