Cyclic guanosine monophosphate: effects on short-circuit current and water permeability

In the isolated toad bladder, cyclic guanosine monophosphate induces an increase in short-circuit current similar to that produced by cyclic adenosine monophosphate. In contrast, cyclic guanosine monophosphate has no effect on water permeability in this organ. This finding raises the possibility that different and independent intra-cellular secondary messengers may exist.