[The role of cyclic AMP and Ca in the altered permeability of tumour cells grown with a deficiency of Mg].

Yoshida-Ascites tumour cells grown with a deficiency of Mg show an increased passive permeability. This results in an accelerated efflux of Na+. The uptake of aminobutyric acid is decreased, while its release is unchanged. The uptake and release of alpha-methylglucopyranoside are unchanged. In the cells grown with a deficiency of Mg, the concentration of cyclic AMP is slightly increased. The addition of dibutyryl cyclic AMP results in similar but smaller changes in the cellular concentration of cations, to those found in Mg deficiency. It is suggested that the effects of Mg deficiency result from the action of cyclic AMP and/or an increase in the Ca concentration of the cell.