Metabolic co-operation between biochemically marked mammalian cells in tissue culture. 1969.

Cells of a genetic variant of the hamster fibroblast line BHK 21 which lack inosinic pyrophosphorylase activity {IPP~ cells) and therefore cannot normally incorporate [H]hypoxanthine were grown in mixed culture with cells of BHK 21 sublines which have inosinic pyrophosphorylase activity (IPP cells). If not in contact with IPP cells, 1PP~ cells do not incorporate added [H]hypoxanthine into nucleic acid. JPP cells always do incorporate [H]hypoxanthine and IPP~ cells when in direct or indirect contact with IPP cells also incorporate the isotope. Cell to cell contact appears to be essential for this gain of a metabolic function by IPP~ cells. The possible molecular basis and general implications of the phenomenon are discussed.