COMPARATIVE METABOLISM OF RADIUM, STRONTIUM, AND CALCIUM

Abstract

Calcium is one of the most abundant minerals in the vertebrate body and, besides constituting a major portion of the skeletal structure, is known to exert a considerable influence in the normal behavior of certain of the soft tissues. Its relationship to the function of the parathyroid glands, and vitamin D and its role in certain pathological conditions uch as arteriosclerosis and neuro-muscular disorders have been recognized and extensively studied. The comparatively recent advent of isotopic tracers, both stable and radioactive, has been of inestimable value in demonstrating the general dy-namic state of metabolic reactions. Up to the present time, however, the difficulties involved in the char-acterization and production of a radioactive isotope of calcium in quantities uitable for biological ex-perimentation have, unfortunately, precluded a great deal of work with this element. It now appears that the only isotope of calcium suitable for bio-logical tracing is that of mass 45, which has a half life of 180 days and emits a beta particle with a maximum energy of 0.26 Mev. The cyclotron and, more recently the chain-reacting uranium pile, have made limited quantities of Ca 4s, usually in rather low specific activities, available for biological re-search during the past eight years. Studies with radiocalcium and radiostrontium have been done by some investigators under various metabolic conditions to determine the degree of similarity in the behavior of the two. Earlier inves-