Movement of Sodium and Cell Volume Changes in a Sodium-Rich Yeast

Abstract

Sodium-rich yeast was prepared by aerating a yeast suspension in [image]-NaCl for a period of 60 min. This yeast contained then on the average 0.070-0.075 mequiv. Na/g. dry wt. On incubating it with glucose, xylose or lactose in water, 0.1 [image]-KCl or 0.1 [image]-NaCl it lost some of its sodium, in the last case against an apparent concentration gradient. It appears that this movement of Na ion is of a diffusion character as evidenced by the effect of temperature, by incubation without metabolizable substrates and by the use of metabolic inhibitors; however, the possibility of an active contribution to this efflux cannot be excluded. The movement of Na+ out of the cell was shown to be connected with considerable changes of cell volume effected above all by changes of osmotic pressure of the medium, sodium being lost as a 0.06[image] -0.10[image] solution. A discussion of these phenomena is presented.