Total phosphate determination in brain tissues: a method for regional determination of total phosphate in rat brain

A quantitative microassay method is described for brain tissue phosphates. Based on molybdate colorimetric measurements of inorganic phosphate in tissue solutions prepared by acid digestion and high temperature ashing, the method includes the use of calcium to precipitate inorganic phosphate in acid-digested tissues and a correction for contaminants released from porcelain crucibles during the ashing procedure. This method was used to measure the total tissue phosphate concentrations in regional microsamples of rat brain. Averaged values derived from these regional measurements were 100.1 +/- 10.2 mumol/gm wet tissue weight, corresponding closely to whole brain tissue phosphate values reported in the literature. Phosphate concentrations were remarkably uniform in different areas of the cortex and basal ganglia.