Forskolin binding sites in rat liver and brain membranes.

Using [3H]14,15-dihydroforskolin as a radioactive ligand, forskolin binding sites in rat liver and rat brain membranes were identified. Scatchard analysis of binding data revealed equilibrium dissociation constants of 1.6 microM in liver and 0.79 microM in brain membranes. The ligand could be displaced by either forskolin or dihydroforskolin. The maximal number of binding sites in liver and brain was 179 and 3.2 pmol/mg protein, respectively. The question whether these forskolin binding sites are related to the adenylate cyclase stimulating action of the diterpene remains open.