Tissue and species distribution and developmental variation of specific receptors for biologically active phorbol and ingenol esters.

A new and rapid binding assay for [3H]phorbol-12,13-dibutyrate (PDBu) binding to its receptors in cell or tissue homogenates or subcellular fractions is described. PDBu binding sites are widely distributed in mouse tissues. Brain and spleen contain exceptionally high concentrations of these receptors. PDBu receptors are present in all regions of the brain. The choroid plexus and pituitary bind markedly lower amounts of PDBu than other brain regions. Brains or spleens from different murine strains bind almost the same amounts of PDBu while those organs from embryonic mice bind every little PDBu. Binding increases with age and reaches a maximum at approximately 4 weeks of age. Young and mature brains from various species contain these specific binding sites. These data suggest a structural or enzymatic role for PDBu receptors.