Abstract
Inorganic phosphate (Pi) participates in and is a regulator in several metabolic pathways. However, there have been few studies of Pi concentrations inside cells in different tissues in clinical disorders associated with abnormal plasma phosphate. The authors have developed a method that is specific for Pi and applied it to the measurements of intracellular Pi levels in readily accessible human cells, namely, red blood cells, platelets, and leukocytes. Normal ranges for inorganic Pi were as follows: plasma 0.9-1.5 mmol (n = 22); red blood cells 0.6-0.8 mmol; platelets 3.7-4.6 mmol; leukocytes 1.7-2.4 mmol. In a group of patients with vitamin D-resistant rickets (VDRR), the mean Pi in plasma and in all cell types studied was about half that observed in normal persons. These results suggest that there is a widespread reduction in intracellualr Pi in patients with VDDR, even in those without obvious muscle weakness.