Cation transport and content in serum-stimulated CHO-773 cells. III. The intracellular content of sodium, calcium and magnesium

Intracellular sodium, calcium, and magnesium content as well as lithium influx have been examined in serum-stimulated CHO cultures using flame-emission technique. Intracellular sodium and lithium influx does not change during the G1----S transition, they increase by 1.3-2 times in the late S and in mitosis. In stationary cultures of CHO cells cellular magnesium is about 50-60 mumole/gr protein; its content increases in 2-3 hours after serum addition and remains constant during the G1----S transition. In stationary cultures of CHO cells cellular calcium is about 20 mumole/gr protein and it increases by 1.5-2 times in the late G1 and S phases. It is concluded that alterations of ion transport accompany not only the early cell response to mitogen but also the G1----S transition.