Abstract
Phosphorus is prominently associated with mechanisms and structures vital to the maintenance of life in organisms from protozoans to mammals. As phosphate it combines in organic complexes involved in energy transformations within cells. As inorganic phosphate, it associates with calcium in the formation of osseous structures. In higher forms of life, phosphate is demonstrated as a major component in acid-base balance (Pitts and Alexander, 1948; Pitts, 1963). The necessity of phosphate in life functions is clearly seen. However, in comparison to other ions in the extracellular environment such as sodium, potassium and carbonate, phosphate is relatively scarce. Thus, the organism is faced with the essential task of concentrating phosphate within the cellular structures. In the vertebrate groups this task is accomplished by cellular incorporation of phosphate from an extracellular fluid environment. This fluid environment is maintained relatively constant in levels of phosphate concentration. The maintenance is accomplished by humoral regulation. Investigation of the hormonal substances involved in phosphate regulation stemmed from results accomplished in studies on the regulation of calcium levels in the body. It was observed that the substances involved in maintenance of blood calcium levels were apparently also functioning in the regulation of phosphate.