INTAKE AND LOSS OF IONS BY LIVING CELLS. II. EARLY CHANGES OF PHOSPHATE CONTENT OF FUNDULUS EGGS

¹ From the Marine Biological Laboratory, Woods Hole, and Department of Zoology, University of California, Berkeley

Unfertilized eggs of Fundulus heteroclitus were immersed in sea water containing low concentrations (0.193 to 0.25 mM) of radioactive sodium phosphate and the phosphate content in subsequently collected samples after the intervals from one-half minute to one hour was determined by measuring the -radiation from the samples.

It was found that:

(a) The phosphate ion was taken in during two or more periods, separated by periods during which the ion was lost.

(b) During the first rise the permeability was high (6.2-71.8 x 10^-2 moles cm^-2 hr^-1 (Gm L^-1)^-1) while the later rises have lower permeabilities (2.0-4.4 x 10^-2).

(c) The maximum concentrations found in these eggs varied from 0.080 to 1.69 mM or about 1/5 to about 6 times that of the immersion fluid for the respective experiments.

The great rates of penetration (permeabilities) found, considered with the relatively high combining power of the chorion has led to the tentative conclusion that during the first hour or so of such experiments very little phosphate penetrates through the chorion to the egg cell itself.

A tentative theory as to the nature of the processes leading to intake and often accumulation of an ion, its subsequent loss, and repetition of this cycle is proposed. It depends on the assumption that proteins suffer reversibly or irreversibly a "conversion" during ion intake, and that this is due to the action of the ions concerned.