Up-modulation of phorbol dibutyrate receptors by carbachol and arachidonic acid in rat prostatic epithelial cells

Phorbol dibutyrate (PDBu) binding to rat prostatic epithelial cells has been measured as an indirect determination of protein kinase C in this cell system. Analysis of [³H]PDBu binding using competitive displacement demonstrated a single class of PDBu receptors with a Kd=141 nM and a binding capacity of 4.8 pmol PDBu bound/mg cell protein. Raising cytosolic Ca²⁺ levels by redistribution of intracellular Ca²⁺ after cell treatment with carbachol or arachidonic acid (which also affects the bulk biophysical properties of the cell membrane) resulted in up-regulation of the available number of PDBu receptors. These results appear to be a consequence of PKC translocation from the cytosolic compartment to the plasma membrane after a cytosolic Ca²⁺ increase, confirming previous results in other cell systems.