Radioactive phosphate concentration in the cerebral cortex

Abstract

The laminar distribution of P32 was studied by radioautography and direct tissue analysis in the parietal cortex of the cat thirty minutes to twenty-one days after a single intravenous injection of the isotope. Similar studies were undertaken in the parietal cortex of human brains recovered at autopsy four to twenty-nine days after the administration of P32. During the first hour, P32 concentrates mostly in laminae I and II. Later, the zone of high concentration gradually involves laminae III and IV and eventually the entire cortex and subcortical white matter. The concentration gradient from surface to depth diminishes with time but is still noticeable four weeks after injection. The pattern of P32 deposition cannot be explained by the volume of cells in various cortical laminae. In spite of its superficial resemblance to the laminar distribution of a number of enzymes, the P32 concentration in various layers of the cortex is apparently determined to a great extent by its physical diffusion from the cerebrospinal fluid.