No abstract

56BIOCHEMICAL SOCIETY TRANSACTIONS activity contributed little to the T K levels in the partially replaced medium. It is possible that T K 2 may be relatively more stable than T K 1 and accumulates with time, though it should be noted that T K activities in partially replaced medium were not higher relative to cell counts than was observed when the entire medium was replaced daily.T h e results described would indicate that proliferating cells in culture release T K into the surrounding medium. While direct extrapolation to in vivo conditions is impossible, these results suggest that the elevated T K levels found in the serum of patients with certain cancers may at least partially be the result of release of T K into the peripheral blood stream from the rapidly proliferating tumour cells.