Studies in Mineral Metabolism with the Aid of Artificial Radioactive Isotopes: VI. Cobalt.

Prior to 1935, studies on the absorption of phosphorus were carried out either by the use of intestinal fistulas, or by the addition of an inactive unabsorbed marker to the food, such as iron oxide in the method of Bergeim (1). Recently the excretion of calcium and phosphorus into the large intestine of the rabbit has been studied by Cowell (2) by means of the differential analysis of fecal pellets and changes in the concentrations of these elements from cecum to anus. With the discovery of induced radioactivity (3), and the preparation of the radioactive phosphorus isotope of atomic weight 32 (4), it has become possible to investigate the rates of absorption, distribution, and excretion of phosphorus, and the percentages involved. One can now distinguish the administered phosphorus from that present in the animal under investigation (5, 6). Hevesy, in 1923, demonstrated the use of radioactive isotopes as indicators in biological investigations (7), and Chiewitz and Hevesy were the first to use the Ps2 isotope in studies of phosphorus metabolism (6, 8). Since then, with the invention and development of the “cyclotron” by Lawrence and collaborators (9, lo), and the resultant availability of “radiophosphorus,” work has been published on certain phases of phosphorus storage and elimination (6, 8, ll-13), on the rate of phospholipid synthesis (14-17), and upon the locale of this synthesis (17).