Effect of fluoride on the phosphodiesterase of bovine photoreceptors.

In the absence of the specific hormone, fluoride is able to activate the adenylate cyclase because it interacts with the GTP-binding protein. It has been reported that fluoride activates also the phosphodiesterase of the light-sensitive enzymatic cascade in dark-adapted retinal rod outer segments, but there is no indication that the GTP-binding protein is involved in this process or not. We show here that also in the photoreceptor system fluoride does interact with the GTP-binding protein in order to activate the phosphodiesterase in the dark. Further, we show evidences that fluoride solubilizes the GTP-binding protein in the dark and that the resulting complex activates the phosphodiesterase in dark-adapted rod outer segment membranes.