Molybdenum metabolism and interrelationships with copper and phosphorus.

In 1938 it was discovered that naturally occurring molybdenum in certain pastures in the United Kingdom was responsible for a severe disease of cattle and sheep (1). The unhealthy pastures were characterized by a molybdenum content of 20 to 1.00 parts per million on the dry basis, as compared with less than 5 p.p.m. in the normal pasture. The experimental production of the disease by administration of sodium molybdate to healthy cattle confirmed the toxic action of this element. The literature on molybdenum in relation to the health of farm animals has been reviewed to 1944 by Russell (2). Potentially toxic levels of molybdenum have since been reported in parts of Florida and California (3, 4).1 A most satisfactory feature of the molybdenum problem has been the finding that supplemental copper will apparently cure or prevent the condition. The symptoms of this disease are remarkably similar to those of copper deficiency,’ and the therapeutic action of copper indicates a relationship between these two elements which is as yet unexplained. An outstanding symptom of copper deficiency or copper-molybdenum imbalance is the interference with normal bone development. This observation, in addition to the findings that alkaline blood phosphatase values in cattle were affected by the copper status of the animal (5), and that molybdenum metabolism was similar to that of phosphorus, has indicated that phosphorus may also be involved in the copper-molybdenum antagonism. Molybdenum Tosicity-Fairhall et al. (6) have presented a comprehensive compilation of the literature on molybdenum up to 1945 and described an experimental study of its toxicity. It was found that soluble molybdenum compounds when fed to rats and guinea pigs in large doses of from 1200 to 6000 mg. per kilo of body weight invariably proved fatal;