Intake and Loss of Radioactive Cations by Certain Marine Eggs. ∗

Abstract

In another paper, 1 three phases of intake of radioactive alkali metal ions by Nitella 2 have been provisionally identified. Most of the intake and loss of ions by the protoplasm of Nitella appears to be in the nature of ion exchange. In the first few minutes the inorganic ions present in the protoplasm before the experiment are replaced by “tagged” ions, these ions moving at rates approximately 1 × 10⁻⁷ GM.cm⁻²sec⁻² like that of water, rather than the previously supposed rates of 1 × 10⁻⁹ or thereabouts. This is the process termed “induced accumulation”. 3 The total amount of ions corresponds approximately to the number of available salt linkages in the known volume of the protoplasm. The following loss of ions is subsequently encountered repeatedly, and it may be surmised to be due to the displacement of the tagged ions from protoplasmic salt linkages by organic ions produced in metabolism. The ions used, Na, K, and Rb, are known to modulate some phases of metabolism. The organic ions so produced appear to be replaced by tagged ions from the surrounding medium, giving “primary accumulation”. 3 The presence of interrelated slow and fast processes may account for the periodic oscillation of the tagged ion content of the protoplasm found throughout at least 110 hours.

Similar experiments were done with eggs of Urechis caupo, Pisaster ochraceus and Patiria miniata. The induced accumulation of ions is shown in Table I, which also shows the calculated number of salt linkages in the same volume of protoplasm. This shows correspondence between the equivalents of cations taken up by induced accumulation and the calculated salt linkages of the protoplasm. The latter figures were obtained from the observed amounts of protein and fat in these eggs. 4