Effects of high ZnSO4 center dot 7H(2)O supplementation on cell growth and monoclonal antibody (mAb) production in chemically defined suspension cultures of recombinant Chinese hamster ovary (rCHO) DG44 cells were examined. The supplementation of ZnSO4 center dot 7H(2)Oup to 120 mu M gradually increased specific mAb production rate of rCHO DG44 cells in the early growth phase (0-4 days of culture). The ZnSO4 center dot 7H(2)O concentration for enhancing mAb production without any cytotoxic effects on cell growth was 30-60 mu M. In addition of 60 mu M ZnSO4 center dot 7H(2)O to in-house protein-free medium and in-house chemically defined medium, mAb production was increased 2.0-fold and 6.5-fold, respectively. Moreover, addition of ZnSO4 center dot 7H(2)O to three kinds of commercial chemically defined media yielded a greater than 1.2-fold enhancement of mAb production. These data indicate that simple supplementation of a relatively high zinc ion concentration to cell culture media without significant changes of rCHO DG44 cell culture process can be useful for achieving high production of mAb.