Radioactivity and Physiology

H. Zwaardemaker. On physiological radio-activity. Journal of Physiology. Vol. LIII, p. 273 (1920).

Over the last five years the Utrecht physiologist Zwaardemaker has made a whole series of reports on his work in the field of radioactive phenomena as a basis for processes in the living organism. The indicated article gives a brief summary of these works. In the human body, chiefly in the cells of the muscles and red blood corpuscles, there are 40 grams of potassium. In addition to this amount fixed in the cells, our blood contains about 1 gram of potassium in the form of free ions. According to the author’s view, this potassium circulating in the blood is capable of producing a radioactive effect; that potassium in general has radioactive properties and belongs to the light radioactive elements, like rubidium, and also caesium, was proved by Campbell and Wood. The starting point for Zwaardemaker is the following fact, established by him and his collaborators in a series of experiments. It is known that if potassium chloride is absent from the so-called Ringer’s fluid, then a frog’s heart perfused with such a fluid ceases to contract. The addition of potassium in the appropriate dose again causes contraction of the heart. Ringer had already indicated that one may take rubidium, the neighbor of potassium in the periodic system, and in the solution thus obtained the heart works indefinitely long. Zwaardemaker goes further and draws attention to the fact that the replacement of potassium in Ringer’s fluid by rubidium depends not on the chemical proximity of these metals, but on the fact that both are radioactive. The favorable action on the heart of potassium and rubidium is thus attributed to their radioactivity. Zwaardemaker proved by direct experiments that in Ringer’s fluid one may take, in place of potassium, not only rubidium, but also any other heavy radioactive element, such as uranium, thorium, radium, ionium, lanthanum, cerium, niton. The essential point of the author’s entire argument is the circumstance that all these elements mutu-

potassium ion, although they are not related to it in chemical properties and stand far from it in the system of elements, so that their substitution takes place not in equimolecular relations, but precisely in equiradioactive relations. Each of the radioactive elements listed, whether light or heavy, is a substitute for potassium in Ringer’s fluid. A surprising and, in essence, not entirely clear circumstance is that if, into Ringer’s fluid, along with potassium or rubidium, we introduce any one of the listed heavy radioactive elements, the result is not a summation of their effects but, on the contrary, a subtraction. Thus one can prepare a Ringer’s fluid containing potassium chloride and uranyl nitrate in quantities that completely counterbalance one another, and such a fluid will act in the same way as Ringer’s fluid deprived of potassium: both fluids, passed through an excised frog heart, will cause its contractions to stop. Such a heart, as Zwaardemaker maintains, can again be made to work normally if rays issuing from some radioactive element, such as radium or mesothorium, are directed upon it. To a heart that has stopped as a result of the passage of Ringer’s fluid devoid of potassium (or containing, in addition to potassium, a quantity of uranium counterbalancing it), a glass tube containing 5 mg of mesothorium or 3 mg of radium is brought up to a distance of about one centimeter from the heart, and the latter begins to contract. This experiment of stimulating the heart into activity by means of radioactivity is, of all, the most striking, as Zwaardemaker reports. From the further account it appears, however, that this experiment is not always equally successful. Sometimes the contractions are restored three minutes after the beginning of irradiation; sometimes later, only after an hour has elapsed, on average after 28 minutes. In Zwaardemaker’s footsteps other investigators followed as well. Thus, for example, Hamburger, the well-known physiologist in Groningen, showed that Ringer’s reagent deprived of potassium and passed through a frog kidney leads to the renal glomeruli not retaining grape sugar; bringing radium near the kidney restores its property of retaining glucose. We shall give Zwaardemaker’s conclusions in full:

1. In a large number of systems, the potassium atom, with respect to its function, can be replaced by any other radioactive element, heavy or light, in an equiradioactive dose.

2. Substances emitting α-rays and substances emitting β-rays, when applied simultaneously, act oppositely.

3. Potassium (as the carrier of physiological radioactivity) is an irritant for a whole series of cells; it restores and maintains their function if it is brought into contact with the surface of the cells as a free ion contained in the circulating fluid.

4. Free radioactive radiation can replace potassium if the latter has first been removed from the circulating fluid.

A. F. Samoilov.