The
copper complex of
3-ethoxy-2-oxobutyraldehyde bis(
thiosemicarbazone) or
CuKTS is reduced and dissociated upon reaction with Ehrlich cells. Titration of the cells with the complex leads to the specific binding of
copper to
metallothionein with 1 to 1 displacement of its
complement of
zinc. Under conditions of complete titration of
metallothionein, 1.25-2.5 nmol
CuKTS/10(7) cells, cellular
DNA synthesis is rapidly inhibited but no long term effects on cell proliferation are observed. The kinetics of redistribution of Cu and Zn in Ehrlich cells in culture and in animals were studied after pulse reaction of
CuKTS with cells. After exposure of cells to the noncytotoxic concentration of 2.5 nmol of
CuKTS/10(7) cells, nonmetallothionein bound
copper is lost rapidly from the cells, after which
copper in
metallothionein decays. New
zinc metallothionein is made as soon as exposed cells are placed in culture. New synthesis stops when the level of
zinc in
metallothionein reaches control levels. A second pulse treatment of cells with
CuKTS to displace
zinc from
metallothionein again stimulates new synthesis of the
protein to restore its normal concentration. The kinetics of
metal metabolism in Ehrlich cells exposed to 5.5 nmol of
CuKTS/10(7) cells, which inhibits cell proliferation, are qualitatively similar except there is a pronounced lag before new
zinc metallothionein is synthesized. The
Ehrlich ascites tumor in mice responds to
CuKTS similarly to cells in culture. It is also shown that cultured Ehrlich cells do not make extra
zinc metallothionein in the presence of high levels of ZnCl2, and fail to accumulate
copper in the presence of large concentrations of
CuCl2.